Thermoplastic polyimide resin film, multilayer body and method for manufacturing printed wiring board composed of same

ABSTRACT

The present invention provides a laminate having a two-layer or three-layer structure including a non-thermoplastic polyimide film and a thermoplastic polyimide layer provided on one or both of the surfaces thereof, the surface of the thermoplastic polyimide layer being surface-treated; a laminate including a polymer film and a layer provided on one or both of the surfaces thereof, the layer including a polyimide resin composition comprising a polyimide resin with a specified structure and a thermosetting component; and a resin film and a laminate including the same which provided one, at least, of surface having a Ra1 value of arithmetic mean roughness of 0.05 μm to 1 μm measured with a cutoff value of 0.002 mm, and a Ra1/Ra2 ratio of 0.4 to 1, Ra2 being a value measured with a cutoff value of 0.1 mm. These laminates can provide a printed circuit board with excellent adhesiveness, on which a micro-wiring circuit can be formed.

RELATED APPLICATION

This application is a nationalization of PCT applicationPCT/JP2003/015928 filed Dec. 12, 2003 claiming priorities based onJapanese Application No. 2002-362485 filed on Dec. 13, 2002, JapaneseApplication No. 2003-70696 filed on Mar. 14, 2003, and JapaneseApplication No. 2003-71058 filed on Mar. 14, 2003, the content of whichare incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to materials composed of thermoplasticpolyimide resins used for printed wiring boards which are widely usedfor electric and electronic apparatuses, and the like, thermoplasticpolyimide resin films, laminates, and a method for manufacturing printedwiring boards composed of same.

DESCRIPTION OF THE RELATED ART

Recent years, electronic components used for electronic apparatuses havebeen required to have more downsized, higher processing speed, morelighter weight, higher density, higher reliability, and the like withrespect to miniaturization and advancement of electronic apparatuses.Accordingly, a method for packaging semiconductor elements and wiringmaterials and wiring components for mounting semiconductor elements havebeen also required to have higher density, increasingly sophisticatedfunction, and advanced performance. Therefore, recently, wiring boardshave been multilayered, and an additive method has been used as a methodfor forming semiconductor circuits. The additive method is suitable forforming hi-density patterns by means of forming a semiconductor circuitson a substrate by plating such as electroless plating or the like.

However, adhesiveness between a semiconductor circuit comprising a metaland a substrate comprising a resin composition has become a problem withfurther thinning of wiring on a wiring board.

In a method for improving adhesiveness between a plated metal and asubstrate comprising a resin composition, a film-shaped adhesive whichhas a surface to be roughened in a range of arithmetic mean roughness Raof 1 to 10 μm and be subjected to electroless plating is used to permitstrong bonding between the metal and the resin with an adhesive strengthof 10 N/cm or more at the metal-resin interface (refer to, for example,Japanese publication of patent application; Japanese Patent Laid-OpenNo. 11-26933 official report (published on Jan. 29, 1999). This methodcauses no problem when circuit wiring has a high ratio of wiringwidth/wiring space (referred to as “L/S” hereinafter), but the method isunsatisfactory for requirements of further thinning of wiring in future.

Also, circuits have been recently required to have higher density andsmaller thickness with requirements for smaller electronic apparatuseswith sophisticated function. In particular, establishment of a methodfor forming a microcircuit with a L/S of 25 μm/25 μm or less has becomean important problem.

In a printed wiring board, adhesion between a polymer film used as asubstrate and a circuit is generally achieved by surface roughnesscalled an “anchor effect”. Therefore, a step of roughening a surface ofthe film is generally provided for forming roughness of about 3 to 5 μmin terms of a Rz value on the surface of the substrate. Such surfaceroughness of the substrate is not a problem for the formed circuithaving a L/S of 30 μm/30 μm or more, but the roughness is an importantproblem in forming a circuit having a line width with a L/S of 30 μm/30μm or less, particularly 25 μm/25 μm or less. This is because such amicrocircuit line with a high density is affected by the roughness ofthe substrate surface. Therefore, a technique for forming a circuit on apolymer substrate with high surface smoothness is required for forming acircuit with a L/S value of 25 μm/25 μm or less, and the smoothness mustbe 3 μm or less and preferably 1.5 μm or less in terms of a Rz value. Inthis case, however, the anchor effect cannot be expected as adhesiveforce, and thus improvement in adhesive strength cannot be expected. Forexample, a method of electroless plating on a roughened surface of anepoxy resin is disclosed as a method for roughening a resin surface(refer to, for example, Japanese publication of patent applicationJapanese Patent Laid-Open No. 2000-198907 official report (published onJul. 18, 2000). However, with a surface roughness Rz of 3 μm or more,high adhesiveness can be achieved, while with a surface roughness Rz of3 μm or less, particularly about 1 μm, an adhesiveness of only about 3N/cm is exhibited. It is thus thought that in the conventional method ofroughening a film surface, high surface roughness is required forexpecting the anchor effect. Therefore, it has become necessary todevelop another adhesion method.

For example, with respect to improvement in adhesiveness to circuitwiring formed on a resin surface having small surface roughness, atechnique for improving the adhesiveness by adding a titanium-basedorganic compound in a polyimide film, likewise polyimide coated with ametal salt comprising Sn, Cu, Zn, Fe, Co, Mn, or Pd to be improved insurface adhesive force, and the like are disclosed (refer to, forexample, Japanese publication of patent application; Japanese PatentLaid-Open No. 6-73209 official report (published on Mar. 15, 1994)(U.S.Pat. No. 5,227,224), and Japanese Patent No. 1,948,445 (U.S. Pat. No.4,742,099)). Also, a method of metallizing a polyimide film produced byapplying a heat-resistant surface treatment agent to a solidifiedpolyamic-acid film and then imidizing, is disclosed (refer to, forexample, U.S. Pat. No. 5,130,192). Furthermore, a method of applyingtitanium elements on a surface of a polyimide film is disclosed (referto, for example, Japanese publication of patent application; JapanesePatent Laid-Open No. 11-71474 official report (published on Mar. 16,1999). Furthermore, a method is disclosed, in which an intermediatelayer is formed on a surface of resin molded product by vapor phasepolymerization of oxydianiline and pyromellitic dianhydride used as araw material of polyimide, and then metallized by vacuum vapordeposition (refer to, for example, Japanese publication of patentapplication; Japanese Patent Laid-Open No. 2002-192651 official report(published on Jul. 10, 2002) and International Publication No. 03/006553pamphlet). Also, the present inventors disclose a method for enhancingadhesive strength between polyimide and an adhesive layer, in which aconductor layer is formed on a thermoplastic polyimide surface by dryplating, and then fusion-bonded thereto by pressing and heat treatment(refer to, for example, Japanese publication of patent applicationJapanese Patent Laid-Open No. 2002-113812 official report (published onApr. 16, 2002). In order to improve adhesiveness of a metal foil, amethod of bonding thermoplastic polyimide to the metal foil is disclosed(refer to, for example, Japanese publication of patent application;Japanese Patent Laid-Open No. 8-230103 official report (published onSep. 10, 1996).

A copper metal layer formed on a surface of the above-describedpolyimide film by a physical method such as vacuum evaporation,sputtering, or the like has higher adhesive strength than that of acopper metal layer formed on a surface of an ordinary polyimide film.However, the use of a vacuum process causes the disadvantage ofincreasing the cost in manufacturing process.

On the other hand, circuit substrates have been required to havehigher-density micro-wiring, improved adhesiveness between a polymerfilm and the microcircuit wiring, and dimensional stability underseverer environments of high temperature and high humidity. Inparticular, the adhesion between the polymer film and the circuit wiringhas been required to resist in high-temperature, high-humidityenvironments.

Furthermore, in a printed wiring board with circuits formed on bothsurfaces thereof, formation of via holes is indispensable for conductingboth surfaces of the wiring board. Therefore, in such a printed wiringboard, circuits are generally formed through a step of forming the viaholes using a laser, a desmearing step, a catalyst application step, anelectroless copper plating step, and the like.

A microcircuit is formed by a so-called subtractive method comprisingsteps of forming a resist film, electroplating copper on a portion inwhich an electroless-plated film is exposed, removing the resist film,and etching off the excess electroless-plated copper film, or asemi-additive method comprising steps of forming a resist film,electroplating copper on a portion in which an electroless-plated filmis exposed, removing the resist film, etching off the excesselectroless-plated copper film. Therefore, of course, the adhesivenessbetween the wiring circuit and the polymer film must resist theseprocesses.

As described above, for a film having low surface roughness, there hasnot been found yet a material with which sufficient adhesive strengthcan be obtained without using a high-cost method or complicated method,and adhesive strength can be maintained in an environment of hightemperature and high humidity, and which can resist a process formanufacturing a wiring board.

DISCLOSURE OF INVENTION

The present invention relates to a material including a thermoplasticpolyimide resin surface-treated to exhibit an adhesive strength of 5N/cm or more when an electroless-plated film is formed on a surfacethereof.

The surface treatment as above is preferably surface treatment forforming roughness on a surface of a thermoplastic polyimide resin film,surface treatment for partially removing a surface layer of thethermoplastic polyimide resin film, or a combination of the surfacetreatment for forming roughness on a surface of the thermoplasticpolyimide resin film and the surface treatment for partially removing asurface layer of the thermoplastic polyimide resin film.

The surface-treated thermoplastic polyimide resin preferably has asurface with a ten-point medium height Rz of 3 μm or less.

The thermoplastic polyimide resin is preferably produced by dehydrationand ring closure of a polyamic acid represented by formula (1):

(wherein A represents at least one tetravalent organic group selectedfrom the group (2) below, and X represents a divalent organic groupselected from the group (3) below).

Also, the present invention relates to a laminate comprising anon-thermoplastic polyimide film and a layer provided on one of thesurfaces thereof, the layer comprising the material including thethermoplastic polyimide resin.

Furthermore, the present invention relates to a laminate comprising anon-thermoplastic polyimide film, a layer provided on one of thesurfaces thereof, the layer comprising the material including thethermoplastic polyimide resin, and a layer comprising the materialincluding the thermoplastic polyimide resin, a copper foil, or anadhesive layer provided on the other surface.

The thickness of the surface layer comprising the material including thethermoplastic polyimide resin and formed on the non-thermoplasticpolyimide is preferably 10 μm or less and smaller than that of thenon-thermoplastic polyimide film.

Furthermore, the present invention relates to a laminate comprising apolymer film and a layer provided on at least one of the surfacesthereof, the layer comprising a polyimide resin composition containing athermoplastic polyimide resin and a thermosetting component, and thethermoplastic polyimide resin having a structure represented by formula(2):

(wherein m is an integer of 1 or more; n is an integer of 0 or more; Vrepresents —O—, —O-T-O—, or —C(═O)—O-T-O(C═O)—; T represents a divalentorganic group; Y's may be the same or different and each represent—C(═O)—, —SO₂—, —O—, —S—, —(CH₂)_(b)—, —NHCO—, —C(CH₃)₂—, —C(CF₃)₂—,—C(═O)O—, or a single bond; a and b independently represent an integerof 0 to 5; Z represents —C(═O)—, —SO₂—, —O—, —S—, —(CH₂)_(d)—, —NHCO—,—C(CH₃)₂—, —C(CF₃)₂—, —C(═O)O—, or a single bond; c and d independentlyrepresent an integer of 0 to 5, and X's may be the same or different andeach represent an independent functional group containing at least onefunctional group selected from —OH, —COOH, —OCN, and —CN).

A film or adhesive layer comprising a polyimide resin compositionincluding a thermoplastic polyimide resin and a thermosetting componentis preferably provided on the surface opposite to the surface on whichthe layer comprising the polyimide resin composition containing thethermoplastic polyimide resin and the thermosetting component isprovided.

Furthermore, present invention relates to a resin film having a surfaceroughness formed on at least one of the surfaces thereof, the surfaceshape having an arithmetic mean roughness Ra1 value of 0.05 μm to 1 μmmeasured with a cutoff value of 0.002 mm, and a Ra1/Ra2 ratio of 0.4 to1, Ra2 being a value measured with a cutoff value of 0.1 mm.

The resin film preferably contains a polyimide resin.

Furthermore, the present invention relates to a laminate comprising atleast one layer of the resin film as above.

A metal layer is preferably formed on the surface having theabove-described surface shape.

The present invention relates to a method for manufacturing a printedwiring board using the laminate or the resin film.

The method preferably includes at least a step of electroless copperplating.

The method preferably includes a step of opposing a metal foil to thesurface of the above-described laminate on which the layer comprisingthe polyimide resin composition containing the thermoplastic polyimideresin and/or the thermosetting component is formed, opposing a circuitplane of an inner wiring board to the other surface with an adhesiveprovided therebetween, laminating the metal foil, the laminate, and theinner circuit board by a method under heating and/or pressing to form alaminate, and removing the metal foil from the surface of the laminate.

The method preferably comprises at least a step of forming a metal layerby sputtering.

A circuit is preferably formed by a subtractive process or asemi-additive process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing an example of the constitution of thepresent invention.

FIG. 2 is a drawing showing an example of the constitution of thepresent invention.

FIG. 3 is a drawing showing an example of the constitution of thepresent invention.

FIG. 4 is a drawing showing an example of the constitution of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail below.

In an embodiment of the present invention, a material containing athermoplastic polyimide resin is subjected to specified surfacetreatment to improve adhesive strength and exhibit sufficiently higheradhesive strength than that expected as an anchor effect regardless ofits low surface roughness, as compared with conventional materials suchas epoxy resin and the like.

The thermoplastic polyimide has a glass transition temperature and canbe plastically molded in a temperature range of the glass transitiontemperature or more apart from a so-called non-thermoplastic polyimidesynthesized from, for example, pyromellitic dianhydride andoxydianiline.

The material containing the thermoplastic polyimide resin of the presentinvention preferably comprises only the thermoplastic polyimide resin,but it may contain other components, such as a thermosetting componentused for an adhesive layer, which will be described below. The contentof the thermoplastic polyimide resin is preferably 30 mol % or more andmore preferably 50 mol % or more. When the content of the thermoplasticpolyimide resin is less than 30 mol %, sufficient adhesive strengthcannot be obtained with an adhesive layer having low surface roughness.

The thermoplastic polyimide resin used in the present invention ispreferably produced by dehydration and ring closure of a polyamic acidrepresented by formula (1):

wherein A is preferably at least one tetravalent organic group selectedfrom the following group (2):

Also, X in formula (1) is preferably at least one selected from thefollowing group (3):

The thermoplastic polyimide resin represented by formula (1) issynthesized from an acid dianhydride compound and a diamine compoundused as raw materials. Examples of the acid dianhydride for producingthe thermoplastic polyimide include tetracarboxylic dianhydrides such aspyromellitic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylicdianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride,2,2′,3,3′-biphenyltetracarboxylic dianhydride,2,3,3′,4′-biphenyltetracarboxylic dianhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride, oxydiphthalicdianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride,bis(3,4-dicarboxyphenyl)methane dianhydride,1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride,1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride,1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,1,3-bis(3,4-dicarboxyphenyl)propane dianhydride,4,4′-hexafluoroisopropylidenediphthalic anhydride,1,2,5,6-naphthalenetetracarboxylic dianhydride,2,3,6,7-naphthalenetetracarboxylic dianhydride,3,4,9,10-perylenetetracarboxylic dianhydride, p-phenylenebis(trimelliticacid monoester anhydride), ethylenebis(trimellitic acid monoesteranhydride), bisphenol A bis(trimellitic acid monoester anhydride),4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride), andp-phenylenediphthalic anhydride. Preferably, at least one dianhydride isselected from these compounds.

As the diamine for obtaining the thermoplastic polyimide, at least onediamine is preferably selected from1,4-diaminobenzene(p-phenylenediamine), 1,3-diaminobenzene,1,2-diaminobenzene, benzidine, 3,3′-dichlorobenzidine,3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine,3,3′-dihydroxybenzidine, 3,3′,5,5′-tetramethylbenzidine,4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylhexafluoropropane,1,5-diaminonaphthalene, 4,4′-diaminodiphenyldiethylsilane,4,4′-diaminodiphenylsilane, 4,4′-diaminodiphenylethylphosphine oxide,4,4′-diaminodiphenyl-N-methylamine, 4,4′-diaminodiphenyl-N-phenylamine,4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,3,3′-diaminodiphenyl ether, 4,4′-diaminodiphenyl thioether,3,4′-diaminodiphenyl thioether, 3,3′-diaminodiphenyl thioether,3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone,3,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone,4,4′-diaminobenzanilide, 3,4′-diaminobenzanilide,3,3′-diaminobenzanilide, 4,4′-diaminobenzophenone,3,4′-diaminobenzophenone, 3,3′-diaminobenzophenone,bis[4-(3-aminophenoxy)phenyl]methane,bis[4-(4-aminophenoxy)phenyl]methane,1,1-bis[4-(3-aminophenoxy)phenyl]ethane,1,1-bis[4-(4-aminophenoxy)phenyl]ethane,1,2-bis[4-(3-aminophenoxy)phenyl]ethane,1,2-bis[4-(4-aminophenoxy)phenyl]ethane,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]butane,2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene,1,4-bis(4-aminophenoxy)benzene, 4,4′-bis(4-aminophenoxy)biphenyl,4,4′-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone,bis[4-(4-aminophenoxy)phenyl]ketone,bis[4-(3-aminophenoxy)phenyl]sulfide,bis[4-(4-aminophenoxy)phenyl]sulfide,bis[4-(3-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether,1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,1,3-bis[4-(3-aminophenoxy)benzoyl]benzene,4,4′-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether,4,4′-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone,bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone,1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene,1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene,4,4′-diaminodiphenylethylphosphine oxide,1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

Among combinations of these acid dianhydrides and diamines for obtainingthe thermoplastic polyimide resin of the present invention, a preferredcombination includes at least one acid dianhydride selected from aciddianhydrides producing the acid dianhydride residues in group (2) and atleast one diamine selected from diamines producing the diamine residuesin group (3). At least one acid dianhydride selected from aciddianhydrides producing the acid dianhydride residues in group (2) ispreferably used in an amount of 50 mol % or more of a total of aciddianhydrides, and at least one diamine selected from diamines producingthe diamine residues in group (3) is preferably used in an amount of 50mol % or more of a total of diamines.

Among the above-described acid dianhydrides and diamines,2,3,3′,4′-biphenyltetracarboxylic dianhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride, oxydiphthalicdianhydride, ethylenebis(trimellitic acid monoester anhydride),bisphenol A bis(trimellitic acid monoester anhydride), and4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) are morepreferred. Also, 1,3-diaminobenzene, 3,4′-diaminodiphenyl ether,4,4′-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene,1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene,2,2-bis[4-(4-aminophenoxy)phenyl]propane,4,4′-bis(4-aminophenoxy)biphenyl, andbis[4-(4-aminophenoxy)phenyl]sulfone are more preferred. This is becausethese acid dianhydrides and diamines are industrially available andproduce thermoplastic polyimides having excellent properties such as lowwater absorption, low dielectric constants, low dielectric losstangents, etc., and also exhibit the effect of increasing adhesivestrength to an electroless-plated film, which is the advantage of thepresent invention.

A polyamic acid which is a precursor of the thermoplastic polyimide usedin the present invention is obtained as a polyamic acid in organicsolvent solution prepared by dissolving substantially equal moles of atleast one of the above acid dianhydrides and at least one of the abovediamines in an organic solvent, and then performing reaction.

The thermoplastic polyimide resin can be produced by imidizing thepolyamic acid, which is a precursor, by either a thermal curing methodor a chemical curing method. In the thermal curing method, imidizationreaction is progressed only by heating without using a dehydration-ringclosure agent or the like. Specific example of this method includesheat-treating the polyamic acid solution to progress the imidizationreaction, and, at the same time, evaporating the organic solvent. Thismethod can produce the solid thermoplastic polyimide resin. Although theheating conditions are not particularly limited, heating process ispreferably performed at a temperature range of 300° C. or less for atime of about 5 minutes to 200 minutes.

In the chemical imidizing method, a chemical dehydrating agent such asan acid anhydride, e.g., acetic anhydride or the like, and a catalystsuch as a tertiary amine, e.g., isoquinoline, β-picoline, pyridine, orthe like, are acted on the polyamic acid in organic solvent solution. Aspecific example of this method includes adding a stoichiometic amountor more of the dehydrating agent to the polyamic acid solution to effectdehydration reaction and evaporate the organic solvent. This method canproduce the solid thermoplastic polyimide resin.

Examples of the dehydrating agent used in the chemical curing methodinclude aliphatic acid anhydrides such as acetic anhydride and the like,aromatic anhydrides such as benzoic anhydride and the like,1,3-dichlorohexylcarbodiimide, N,N′-dialkylcarbodiimide, lower aliphatichalides, halogenated lower aliphatic halides, halogenated lower fattyacid anhydrides, arylsulfonic acid dihalides, thionyl halides, andmixtures of two or more of these compounds. Among these compounds,aliphatic acid anhydrides such as acetic anhydride, propionic anhydride,and butyric anhydride, or mixtures of two or more of these compounds arepreferably used. The chemical conversion agent is used in an amount of 1to 10 times, preferably 1 to 7 times, and more preferably 1 to 5 times,to the number of the moles of the polyamic acid sites in the polyamicacid solution. In order to perform effective imidization, the chemicalconversion agent and the catalyst are preferably used at the same time.Examples of the catalyst include aliphatic tertiary amines such astriethylamine and the like, aromatic tertiary amines such asdimethylaniline and the like, and heterocyclic tertiary amines such aspyridine, α-picoline, β-picoline, γ-picoline, quinoline, andisoquinoline and the like. In particular, the catalyst is preferablyselected from the heterocyclic tertiary amines. The catalyst is added inan amount of 1/20 to 10 times, preferably 1/15 to 5 times, and morepreferably 1/10 to 2 times, to the number of the moles of the chemicalconversion agent. With excessively small amounts of the chemicalconversion agent and the catalyst, imidization does not effectivelyproceed, while with excessively large amounts of the chemical conversionagent and the catalyst, rapid imidization proceeds to cause difficultyin handling. Furthermore, chemical dehydration and ring closure arepreferably performed at a temperature of 100° C. or less, and theorganic solvent is preferably evaporated at a temperature of 200° C. orless for a time of about 5 minutes to 120 minutes. Another method forproducing the polyimide resin does not include evaporating the solventin the thermal or chemical dehydration and ring closure. Specifically, athermoplastic polyimide resin solution prepared by thermal imidizationor chemical imidization using a dehydrating agent is poured into a poorsolvent to precipitate the thermoplastic polyimide resin, unreactedmonomers are removed, and then the resulting polyimide resin is purifiedand dried to obtain the solid thermoplastic polyimide resin. As the poorsolvent, a solvent having high compatibility with the solvent and lowdissolving power for the polyimide is selected. Examples of the solventinclude, without limitation to, acetone, methanol, ethanol, isopropanol,benzene, methyl cellosolve, and methyl ethyl ketone.

A method of imidization by heating under reduced pressure can also beused. This imidization method is capable of positively removing thewater produced in imidization to the outside of the system to suppressthe hydrolysis of a polyamic acid polymer, and thereby obtaining ahigh-molecular-weight thermoplastic polyimide.

In the method of imidization by heating under reduced pressure, heatingis preferably performed at 80 to 400° C., more preferably 100° C. ormore and most preferably 120° C. or more, for effective imidization andeffective removal of water.

The reduced pressure is preferably as low as possible. Specifically, thepressure is 9×10⁴ to 1×10² Pa, preferably 9×10⁴ to 1×10² Pa, and morepreferably 7×10⁴ to 1×10² Pa.

Furthermore, the chemical curing method and the thermal curing methodmay be combined. The imidization conditions may be appropriatelydetermined according to the type of the polyamic acid used, the form ofthe resultant resin, selection of the thermal curing method and/or thechemical curing method, etc.

Examples of the solvent used in reaction for producing the polyamic acidpolymer solution include sulfoxide solvents such as dimethylsulfoxideand diethylsulfoxide and the like; formamide solvents such asN,N-dimethylformamide and N,N-diethylformamide and the like; acetamidesolvents such as N,N-dimethylacetamide and N,N-diethylacetamide and thelike; pyrolidone solvents such as N-methyl-2-pyrolidone andN-vinyl-2-pyrolidone and the like; phenol solvents such as phenol, o-,m-, or p-cresol, xylenol, halogenated phenol, catechol and the like;hexamethylphosphoramide; and γ-butyrolactone. Among these solvents,N,N-dimethylformamide is particularly preferably used. Furthermore, suchan organic polar solvent may be combined with an aromatic hydrocarbonsuch as xylene or toluene according to demand. A mixture of the aciddianhydride component and the diamine component is stirred in thesolvent to obtain the polyamic acid polymer solution. For the reaction,the addition order of these raw materials, the reaction time, and thereaction temperature are not particularly limited.

The thermoplastic polyimide resin material produced by the imidizationcan be formed in various shapes such as a molding, a single-layer film,a laminate comprising a layer of the material containing thethermoplastic polyimide resin, the layer being formed on a support, andthe like. In application to a printed wiring board according to thepresent invention, the single-layer film or laminate comprising thethermoplastic polyimide resin is preferred. In the laminate, the supportpreferably comprises a non-thermoplastic polyimide film from theviewpoint of heat resistance, dimensional stability, interfacialadhesiveness, etc. When a copper foil is used as the support, desirablythe copper foil can be used as the support and also used for subsequentsurface treatment of the thermoplastic polyimide resin, which will bedescribed below.

For the laminate according to the present invention, various methods canbe used as a method for forming the layer comprising the thermoplasticpolyimide resin on the heat-resistant non-thermoplastic polyimide filmused as the support.

For example, when the thermoplastic polyimide is insoluble in a solvent,preferably, a solution of a polyamic acid, which is a precursor, isapplied to the non-thermoplastic polyimide film by casting, and thenimidization and solvent drying are performed by the above-describedmethod to form the layer comprising the thermoplastic polyimide resin.When the thermoplastic polyimide is soluble in a solvent, thethermoplastic polyimide resin is formed in a powder, fibers, or a filmand dissolved in a solvent to prepare a thermoplastic polyimidesolution, the solution is applied to the non-thermoplastic polyimidefilm by casting, and the solvent is evaporated by drying to form thelayer comprising the thermoplastic polyimide resin. In this case, as inthe case in which the thermoplastic polyimide is insoluble, the methodof applying the polyamic acid, which is a precursor, to thenon-thermoplastic polyimide film by casting can be used. In anotherapplicable method, a solution of a polyamic acid, which is a precursorof the non-thermoplastic polyimide, and a solution of a polyamide, whichis a precursor of the thermoplastic polyimide, or a solution of thethermoplastic polyimide are coextruded and subjected to imidization andsolvent evaporation to form a laminate comprising a layer of thethermoplastic polyimide resin and a layer of the non-thermoplasticpolyimide film. A further applicable method for forming the laminatecomprises producing a film of the thermoplastic polyimide resin, andlaminating the film on the non-thermoplastic polyimide film by a knownlamination method such as pressing, lamination, or the like.

The non-thermoplastic polyimide film used in the present invention canbe produced by a known method. Namely, the polyamic acid is applied tothe support by casting, and then chemically or thermally imidized toobtain the non-thermoplastic polyimide film.

As the polyamic acid which is a precursor of the non-thermoplasticpolyimide used in the present invention, basically, any known polyamicacid can be used.

Suitable examples of the acid anhydride for synthesizing thenon-thermoplastic polyimide used in the present invention include theacid anhydrides described for the thermoplastic polyimide, and theanalogues thereof. In particular, pyromellitic dianhydride,oxydiphthalic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylicdianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, andp-phenylenebis(trimellitic acid monoester anhydride) are preferred.These anhydrides are preferably used alone or in a mixture at a desiredratio.

Examples of the diamine used for synthesizing the non-thermoplasticpolyimide in the present invention include the same diamines as thosedescribed for the thermoplastic polyimide, and the analogues thereof. Inparticular, 4,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide,p-phenylenediamine, and p-phenylenebis(trimellitic acid monoesteranhydride), and mixtures thereof.

Examples of a preferred combination of the acid dianhydride and thediamine for the non-thermoplastic polyimide film of the presentinvention include pyromellitic dianhydride/4,4′-diaminodiphenyl ether,pyromellitic dianhydride/4,4′-diaminodiphenyl ether/p-phenylenediamine,pyromellitic dianhydride/p-phenylenebis(trimellitic acid monoesteranhydride)/4,4′-diaminodiphenyl ether/p-phenylenediamine,p-phenylenediamine/3,3′,4,4′-biphenyltetracarboxylic dianhydride, and3,3′,4,4′-biphenyltetracarboxylic dianhydride/p-phenylenebis(trimelliticacid monoester anhydride)/p-phenylenediamine/4,4′-diaminodiphenyl ether.Since the non-thermoplastic polyimide synthesized by such a monomercombination exhibits excellent properties such as appropriate elasticmodulus, likable dimensional stability, low water absorption, and thelike, the non-thermoplastic polyimide is suitably used for the laminatein the present invention.

Synthesis of the polyamic acid and synthesis of polyimide by imidizationof the polyamic acid can be performed under the same conditions as thosefor synthesizing the thermoplastic polyimide. However, from theviewpoint of film toughness, breaking strength, and productivity, thechemical curing method is preferred as the imidization method.

The non-thermoplastic polyimide film produced by any of the variousmethods may be mixed with an inorganic or organic filler, a plasticizersuch as an organophosphorus compound, an antioxidant by a known method,or may be surface-treated by known physical surface treatment such ascorona discharge treatment, plasma discharge treatment, or ion guntreatment, or chemical surface treatment such as primer treatment toimpart more excellent characteristics.

The non-thermoplastic polyimide resin is produced using the same aciddianhydride and diamine as those for the thermoplastic polyimide resin.However, the thermoplastic polyimide resin has a glass transitiontemperature and can be plastically deformed by heating at the glasstransition temperature or more. While the non-thermoplastic polyimideresin can not be easily plastically deformed by heating regardless ofthe presence of a glass transition temperature. Therefore, bothpolyimide resins are different.

Although a polyimide resin can be produced by reaction of at least oneacid anhydride and at least one diamine, the thermoplastic polyimideresin or the non-thermoplastic polyimide resin can be produced byappropriately selecting the types of the acid anhydride and diamine, themixing ratio of a plurality of acid anhydrides, the mixing ratio of aplurality of diamines and the lilke when two or more acid anhydrides andtwo or more diamines are used.

In order to obtain the thermoplastic polyimide resin, the acid anhydrideand diamine each having a flexible group or an asymmetric structure maybe selected. When a plurality of acid anhydrides or a plurality ofdiamines is used, the mixing ratio of the acid anhydrides or diamineseach having flexibility or an asymmetric structure may be increased.

The thickness of the non-thermoplastic polyimide film is preferably 2 μmto 125 μm, and more preferably 5 μm to 75 μm. With a thickness of lessthan 2 μm, the laminate has insufficient rigidity, and the film isdifficult to handle. Furthermore, it becomes difficult to form thethermoplastic polyimide layer on the surface of the film. With athickness of over 125 μm, a circuit width must be increased with anincrease in thickness of an insulating layer in view of impedancecontrol, thereby opposing to the need for a smaller printed wiring boardwith a higher density.

Next, the method for surface-treating the thermoplastic polyimide resinof the present invention will be described. The surface-treatedthermoplastic polyimide resin of the present invention is stronglybonded to an electroless-plated film formed on its surface, for example,with an adhesive strength of 5 N/cm or more, preferably 7 N/cm or more,and more preferably 9 N/cm or more. The combination of the thermoplasticpolyimide and suitable surface treatment enables strong bonding of anelectroless-plated copper film in spite of its lower surface roughnessthan conventional roughness. With an adhesive strength of less than 5N/cm, a metal layer separates from the resin surface during manufactureof the printed wiring board, and as a result, the problem of deviatingor dropping out on a wiring circuit tends to occur.

The electroless-plated film can be formed by a known method, preferablyelectroless copper plating, electroless nickel plating, or electrolessgold plating. In particular, the electroless copper plating is preferredfrom the viewpoint of excellent balance between properties such asavailability of chemicals, cost, adhesion to the resin surface,conductivity, processability, and the like.

As a result of several researches, some proper methods for surfacetreatment of the present invention were found. The methods will bedescribed in detail below.

One of the surface treatment methods includes forming irregularity onthe surface of the thermoplastic polyimide resin. It is known thatadhesive strength to the electroless-plated film tends to increase asthe roughness of the irregular surface increases. On the other hand, thepitch of formable wiring tends to increase as the roughness of theirregular surface increases regardless of whether the wiring is formedby the subtractive method or the semi-additive method. Therefore,increases in surface roughness are undesirable for increasing the wiringdensity. In the present invention, the thermoplastic polyimide isselected as a material to be surface-treated, and thus theelectroless-plated film can be strongly bonded in spite of its lowersurface roughness than conventional surface roughness. Therefore, strongadhesion of wiring and formation of finer wiring can be simultaneouslyrealized, thereby complying with the need for a higher-density printedwiring board.

A specific example of the method is a surface treatment method in whichthe thermoplastic polyimide resin and a metal foil having a roughenedsurface are laminated, and then the metal foil is removed. As the metalfoil, any known metal foil can be used. Examples of such a metal foilinclude a copper foil, an aluminum foil, a nickel foil, and a gold foil,but the copper foil which is generally used in a various industrialproducts is advantageous in view of cost and wide variety, and thus canbe preferably used. The metal foil is used for roughening the surface ofthe thermoplastic polyimide resin by a method in which the thermoplasticpolyimide resin and the metal foil are laminated by a known process suchas thermal pressurization, thermal lamination or the like, and then themetal foil is removed by a process of physically peeling the metal foil,dissolving the metal foil, or the like to form a roughened surface onthe thermoplastic polyimide resin. Therefore, the metal foil preferablyhas a roughened surface on at least one of its surfaces.

The roughness of the roughened surface of the metal foil affects theadhesive strength between the thermoplastic polyimide resin and theelectroless-plated film, and the pitch of wiring formable on thethermoplastic polyimide resin. In other words, as the roughness of themetal foil increases, the roughness of the irregular surface formed onthe thermoplastic polyimide resin tends to increase, and also theadhesive strength to the electroless-plated film tends to increase. Onthe other hand, the pitch of formable wiring tends to increaseregardless of whether the wiring is formed by the subtractive method orthe semi-additive method. Thus, increases in roughness are undesirablefor increasing the wiring density. Specifically, the surface roughnessRz (ten-point medium height) of the roughened surface of the metal foilis preferably 3 μm or less, more preferably 2 μm or less, and mostpreferably 1.5 μm or less. This roughness is preferred because thesurface roughness Rz of the irregular surface formed on thethermoplastic polyimide resin is also 3 μm or less, micro-wiring with aL/S of 25 μm m/25 μm or less can be formed, and the adhesive strength is5 N/cm or more. As the copper foil, an electrolytic copper foil and arolled copper foil are widely used, and any one of the copper foils hasa roughened surface, i.e., a matte surface, on at least one surface, forincreasing the adhesive strength to the resin. Also, matte surfaces withvarious degrees of roughness can be obtained using copper foil products,but the matte surface of the rolled copper foil can be preferably usedbecause of its relatively low surface roughness Rz.

Another preferred method for forming irregularity on the surface of thethermoplastic polyimide resin comprises embossing, sand blasting, orpolishing on the surface of the thermoplastic polyimide resin. Embossingcan be performed by bringing the thermoplastic polyimide resin intocontact with a metal material having surface irregularity to formsurface irregularity on the resin surface. The embossing is preferablyaccompanied with heating and pressing, and performed under conditionsfor forming proper irregularity. Also, sand blasting and polishing arepreferably performed under conditions for forming proper irregularity.

A surface treatment method of partially removing the surface layer ofthe thermoplastic polyimide resin can be preferably applied as themethod for surface-treating the thermoplastic polyimide resin. Thissurface treatment method is to dissolve a proper thickness of thesurface of the thermoplastic resin, and thereby the adhesiveness to theelectroless-plated film can be increased. Although the reason for thisis not known, it is understood that by this surface treatment,irregularity is formed on the resin surface and/or the surface layer ofthe thermoplastic polyimide resin is dissolved to change the chemicalstructure, thereby causing a favorable effect on the adhesiveness to theelectroless-plated film. The term “partially removing” means a state inwhich the entire surface layer of the thermoplastic polyimide resin isuniformly removed or a state in which the surface layer is nonuniformlyremoved, i.e., removed or left in an island-like form.

Specific examples of the surface treatment method of partially removingthe surface layer of the thermoplastic polyimide resin include a methodof vapor phase treatment, such as treatment with corona discharge,atmospheric-pressure plasma, vacuum plasma, electron rays, laser, RIE,or the like; and a method of liquid phase treatment, such as treatmentwith a liquid that dissolves the thermoplastic polyimide resin. Thesetreatment methods possibly have the effect of strongly bonding theelectroless-plated film because a fine irregular surface can be formedon the thermoplastic polyimide resin, and also have the effect ofchemically activating the resin surface. Among these treatment methods,the method of vapor phase treatment with corona discharge,atmospheric-pressure plasma, vacuum plasma, or electron rays, and themethod of liquid phase treatment are industrially simple and preferablycarried out. The liquid phase treatment is not particularly limited aslong as the thermoplastic polyimide resin is dissolved to achieve theobject of the present invention. More specifically, a water-solubleliquid containing a permanganate or organic alkali compound, which iswidely used in a desmearing step and etching of polyimide duringmanufacture of the printed wiring board, or an organic solvent ispreferably used. Preferred examples of the organic solvent whichdissolves the thermoplastic polyimide resin include amide solvents, suchas N,N-dimethylformamide, N,N-dimethylacetamide, andN-methyl-2-pyrrolidone. In particular, N,N-dimethylformamide ispreferably used.

The surface treatment method for the thermoplastic polyimide resin andthe specific examples thereof have been described above with respect to“surface treatment for forming irregularity on the surface of thethermoplastic polyimide resin” and “surface treatment for partiallyremoving the surface layer of the thermoplastic polyimide resin”.However, it was found that combination of these methods is alsoeffective. Specifically, “surface treatment for forming irregularity onthe surface of the thermoplastic polyimide resin” and “surface treatmentfor partially removing the surface layer of the thermoplastic polyimideresin” are combined, and various combinations are effective. Inparticular, combination of “surface treatment for forming irregularityon the surface of the thermoplastic polyimide resin” and the liquidphase treatment including dissolving the thermoplastic polyimide resinis particularly effective. More specifically, it is particularlyeffective that the thermoplastic polyimide resin surface-treated withthe metal foil is treated with a permanganate, an organic alkalicompound, or an organic solvent.

The surface roughness Rz of the thermoplastic polyimide resin resultingfrom the above-described surface treatment is preferably 3 μm or lessfrom the viewpoint of forming micro-wiring. With a surface roughness Rzof 3 μm or less, a high-density circuit with a L/S of 25/25 μm or lesscan be formed, and no etching residue remains in the surfaceirregularity of the resin after the etching process. The surfaceroughness Rz is defined according to the surface shape standards of JIS(Japanese Industrial Standards) B0601 or the like. The surface roughnessRz can be measured with a stylus-type surface roughness meter of JISB0651 or an optical interference-type surface roughness meter of B0652.In the invention, the ten-point medium height of the surface of thethermoplastic polyimide resin is measured with an opticalinterference-type surface roughness meter, New View 5030 System,manufactured by ZYGO Corporation.

It was further found that by using the above-mentioned surface treatmentfor the thermoplastic polyimide resin, strong bonding between theelectroless-plated film and a surface with lower roughness thanconventional roughness can be realized, and excellent adhesive strengthcan be maintained after a pressure cooker test. As a result, ahigher-density of printed wiring board, i.e., micro-wiring, can beformed.

Next, a laminate of the present invention will be described below.Namely, description will be made of a two-layer structure laminatecomprising a layer (1) containing the surface-treated thermoplasticpolyimide resin and a non-thermoplastic polyimide film (2), as shown inFIG. 1, a three-layer structure laminate comprising a layer (1)containing the surface-treated thermoplastic polyimide resin, anon-thermoplastic polyimide film (2), and a layer (3) containing thethermoplastic polyimide resin, as shown in FIG. 2, a three-layerstructure laminate comprising a layer (1) containing the surface-treatedthermoplastic polyimide resin, a non-thermoplastic polyimide film (2),and a copper foil layer (4), as shown in FIG. 3, and a three-layerstructure laminate comprising a layer (1) containing the surface-treatedthermoplastic polyimide resin, a non-thermoplastic polyimide film (2),and an adhesive layer (5), as shown in FIG. 4. However, the layer (3)containing the thermoplastic polyimide resin may be a layersurface-treated or not surface-treated.

Any one of the laminates of the present invention comprises the layercontaining the thermoplastic polyimide resin formed on thenon-thermoplastic polyimide film. The non-thermoplastic polyimide film,the thermoplastic polyimide, and the lamination method are as describedabove. The thickness of the layer containing the thermoplastic polyimidein the laminate of the present invention is preferably as small aspossible for making use of the physical properties of thenon-thermoplastic polyimide film having excellent properties as acircuit board, such as low thermal expansion property, heat resistance,electric characteristics, etc. The thickness of the layer containing thethermoplastic polyimide is preferably smaller than that of thenon-thermoplastic polyimide film, more preferably ½ or less and mostpreferably ⅕ or less than that of the non-thermoplastic polyimide film.In the present invention, in some cases, surface irregularity is formedon the thermoplastic polyimide resin by surface treatment. In this case,the thickness of the layer containing the thermoplastic polyimide reinis preferably larger than at least the surface roughness Rz of thesurface of the thermoplastic polyimide resin roughened by surfacetreatment, and preferably at least 2 times the surface roughness Rz. Forexample, when the layer containing the thermoplastic polyimide resinformed on one of the surfaces of the non-thermoplastic polyimide filmhaving a thickness of 25 μm has a surface roughness Rz of 3 μm, thethickness of the layer containing the thermoplastic polyimide resin ispreferably 25 μm, more preferably 12.5 μm, and most preferably about 6μm. The thickness of the non-thermoplastic polyimide film, and thesurface roughness Rz and thickness of the layer containing thethermoplastic polyimide resin formed thereon can be appropriatelycontrolled in a range which does not impair the advantage of the presentinvention.

In the present invention, the copper foil layer in the laminatecomprising the layer containing the surface-treated thermoplasticpolyimide resin, the non-thermoplastic polyimide film, and the copperfoil layer may be formed by bonding directly to a copper foil havingirregularity or bonding to a copper foil with an appropriate adhesive.Instead of the copper foil layer, a copper layer formed by wet platingmay be used. The bonding of the polyimide film and the copper foil withan adhesive can be performed by a known method such as thermallamination, thermal pressing, or the like.

Next, description will be made of the adhesive layer in the laminatecomprising the layer containing the surface-treated thermoplasticpolyimide resin, the layer containing the non-thermoplastic polyimide,and the adhesive layer. Any ordinary adhesive resin can be used as theadhesive, and a known technique which can realize proper resinflowability and high adhesiveness can be used. The adhesive resins usedas the adhesive can be roughly divided into the two types including ahot-melt adhesive type using a thermoplastic resin and a thermosettingadhesive type utilizing curing reaction of a thermosetting resin.

Examples of a thermoplastic resin which imparts hot-melt adhesiveproperty to the adhesive include polyimide resins, polyamide-imideresins, polyetherimide resins, polyamide resins, polyester resins,polycarbonate resins, polyketone resins, polysulfone resins,polyphenylene ether resins, polyolefin resins, polyphenylene sulfideresins, fluorocarbon resins, polyarylate resins, and liquid crystalpolymer resins. These resins can be used alone or in combination of twoor more as the adhesive for the laminate of the present invention. Inparticular, thermoplastic polyimide resins are preferably used from theviewpoint of excellent heat resistance, electric reliability, and thelike. The polyimide resin can be produced using one of known aciddianhydrides or combination of two or more thereof.

In order to exhibit particularly excellent hot-melt adhesive property,ethylenebis(trimellitic acid monoester anhydride),2,2-bis(4-hydroxyphenyl)propane dibenzoate, 3,3′,4,4′-tetracarboxylicdianhydride, 1,2-ethylenebis(trimellitic acid monoester anhydride),4,4′-hexafluoroisopropylidenediphthalic anhydride,2,3,3′,4′-biphenyltetracarboxylic dianhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalicanhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, or4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) ispreferably used.

As the diamine component, known diamines can be used, and the diaminescan be used alone or in combination of two or more. The thermoplasticpolyimide resin used for the laminate of the present invention ispreferably produced using 1,3-bis(3-aminophenoxy)benzene,3,3′-dihydroxybenzidine, or bis(4-(3-aminophenoxy)phenyl)sulfone. Thesecompounds can be used alone or in a mixture at a desired ratio.

Next, the curable adhesive utilizing curing reaction of thethermosetting resin will be described below. Examples of thethermosetting resin include bismaleimide resins, bisallylnadiimideresins, phenol resins, cyanate resins, epoxy resins, acrylic resins,methacrylic resins, triazine resins, hydrosilyl curable resins, allylcurable resins, and unsaturated polyester resins. These resins can beused alone or in appropriate combination. Besides the thermosettingresins, a reactive side chain group-containing thermosetting polymerhaving a reactive group such as an epoxy group, an allyl group, a vinylgroup, an alkoxysilyl group, a hydrosilyl group, a hydroxyl group, orthe like at the side chain or end of the polymer chain can be used asthe thermosetting component. In order to improve the flowability of theadhesive during heat bonding, the thermosetting resin can be mixed withthe thermoplastic resin. In this case, the thermosetting resin ispreferably added in an amount of 1 to 10,000 parts by weight andpreferably 5 to 2,000 parts by weight, relative to 100 parts by weightof the thermoplastic resin. When the amount of the thermosetting resinexceeds 10,000 parts by weight, the adhesive layer may become brittle.On the other hand, when the amount is less than 1 part by weight, theflowability of the adhesive may decrease, or the adhesiveness maydecrease.

As the adhesive for the laminate of the present invention, a polyimideresin, an epoxy resin, a cyanate ester resin, or a blend thereof can bepreferably used from the viewpoint of adhesiveness, processability, heatresistance, flexibility, dimensional stability, low dielectricproperties, cost, etc.

In the present invention, the material and the laminate in any ofvarious forms, each containing the thermoplastic polyimide resin,contain the thermoplastic polyimide resin characterized by beingsurface-treated. However, surface treatment may be performed beforehandon the material or laminate in any of various forms, which contains thethermoplastic polyimide resin, or may be performed during manufacturingprocess of the printed wiring board. For example, the thermoplasticpolyimide resin of the material or laminate containing the thermoplasticpolyimide resin may be subjected to surface treatment, such as “surfacetreatment for forming surface irregularity” and/or “surface treatmentfor partially removing the surface layer”. Alternatively, in the presentinvention, the material containing the thermoplastic polyimide resinbefore surface treatment or the laminate having the material containingthe thermoplastic polyimide resin before surface treatment may be usedfor, for example, manufacturing a printed circuit board, and thensubjected to surface treatment during the manufacturing process. Thesematerials and laminates containing the thermoplastic polyimide resin areincluded in the category of the present invention. More specifically,for example, when a printed wiring board is manufactured using thethree-layer structure laminate comprising the surface-treatedthermoplastic polyimide resin, the non-thermoplastic polyimide film, andthe adhesive layer, a laminate having a structure comprising a metalfoil, a thermoplastic polyimide resin film, a non-thermoplasticpolyimide film, and an adhesive layer, i.e., a laminate comprising ametal foil having surface irregularity, is also included in the categoryof the laminate of the present invention. In this case, the laminatecomprising the metal foil, the thermoplastic polyimide resin film, thenon-thermoplastic polyimide film, and the adhesive layer is laminated onan inner substrate having an inner circuit so that the adhesive layerfaces the inner substrate, and then the metal foil is removed by etchingor the like to perform surface treatment of the thermoplastic polyimideresin. In another specific example in which a laminate comprising asurface-treated thermoplastic polyimide resin film, a non-thermoplasticpolyimide film, and a surface-treated thermoplastic polyimide resin filmis used for manufacturing a printed wiring board, a laminate comprisinga surface-untreated thermoplastic polyimide resin film, i.e., a laminatecomprising a surface-untreated thermoplastic polyimide resin film, asurface-untreated non-thermoplastic polyimide film, and a thermoplasticpolyimide resin film may be used. This laminate is also included in thecategory of the laminate of the present invention. In this case, viaholes are formed in the laminate comprising the surface-untreatedthermoplastic polyimide resin film, the surface-untreatednon-thermoplastic polyimide film, and the thermoplastic polyimide resinfilm by laser, punching, drilling, or the like so that the via holespass through the laminate, and then the laminate is surface-treatedwith, for example, a permanganate solution to perform surface treatmentof the thermoplastic polyimide resin. In this case, preferably,desmearing of the via holes and surface treatment are simultaneouslyperformed.

According to a second embodiment of the present invention, a laminatecomprises a polymer film and a layer formed on at least one of thesurface of the polymer film, and the layer comprises a polyimide resincomposition containing a thermoplastic polyimide resin and athermosetting component. In this laminate, the layer comprising thepolyimide resin composition containing the thermoplastic polyimide resinand the thermosetting component permits strong bonding to a metal layerformed on its surface. Even when a metal foil is laminated on an innerwiring board at low pressure and then removed from the surface thereofin a process for manufacturing a printed wiring board, the surface shapeof the metal foil can be sufficiently transferred because of thepresence of the polymer film. As a result, the degree of freedom oflamination conditions can be increased.

The thermoplastic polyimide resin of the present invention is preferablysoluble. In the present invention, the term “soluble” means a solubilityof 1% by weight or more in at least one solvent selected from dioxolan,dioxane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide,N-methyl-2-pyrrolidone, and the like at a temperature range from roomtemperature to 100° C.

The thermoplastic polyimide resin used in the present invention has astructure represented by formula (2). The content of the structurerepresented by formula (2) is preferably 50 mol %.

The thermoplastic polyimide resin can be produced by dehydration andring closure of a polyamic acid polymer which is produced by reactionbetween an acid dianhydride represented by formula (3) and a diaminecomponent represented by formula (4).

(wherein V represents —O—, —O-T-O—, or —C(═O)—O-T-O—(C═O)—, and Trepresents a divalent organic group).

(wherein Y represents —C(═O)—, —SO₂—, —O—, —S—, —(CH₂)_(b)—, —NHCO—,—C(CH₃)₂—, —C(CF₃)₂—, —C(═O)O—, or a single bond, and a and bindependently represent an integer of 0 to 5).

The content of the acid dianhydride represented by formula (3) ispreferably 50 mol % or more of a total of acid anhydrides. The use ofthe thermoplastic polyimide resin having such a structure has the effectof sufficiently increasing the adhesive strength between a microcircuitformed by a semi-additive method and a polyimide resin composition layercomprising the thermoplastic polyimide resin and the thermosettingcomponent even when the polyimide resin composition layer has a surfaceroughness Rz of 3 μm or less.

Also, an expensive process such as vapor deposition, sputtering, or thelike is not required.

Examples of T in formula (3) include the following:

(wherein Z represents a divalent group selected from the groupconsisting of —C_(Q)H_(2Q)—, —C(═O)—, —SO₂—, —O—, and —S—; and Qrepresents an integer of 1 to 5). Preferably, at least one aciddianhydride is selected from the group consisting of the aciddianhydrides represented by formula (3).

The acid dianhydrides represented by formula (3) can be used alone or incombination of two or more. In formula (3), each benzene ring maycontain a hydrocarbon group such as a methyl group or an ethyl group, ora halogen group such as Br or Cl.

Specific examples of the acid dianhydrides represented by formula (3)include 4,4′-oxydiphthalic anhydride, 3,4′-oxydiphthalic anhydride,3,3′-oxydiphthalic anhydride,4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride),4,4′-hydroquinonebis(phthalic anhydride),2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3′,4,4′-tetracarboxylicdianhydride, 1,2-ethylenebis(trimellitic acid monoester anhydride),p-phenylenebis(trimellitic acid monoester anhydride),4,4′-biphenylenebis(trimellitic acid monoester anhydride),1,4-naphthalenebis(trimellitic acid monoester anhydride),1,2-ethylenebis(trimellitic acid monoester anhydride),1,3-trimethylenebis(trimellitic acid monoester anhydride),1,4-tetramethylenebis(trimellitic acid monoester anhydride),1,5-pentamethylenebis(trimellitic acid monoester anhydride), and1,6-hexamethylenebis(trimellitic acid monoester anhydride). Theseanhydrides can be used alone or in combination. Among these anhydrides,4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride),2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3′,4,4′-tetracarboxylicdianhydride, and 1,2-ethylenebis(trimellitic acid monoester anhydride)can produce thermoplastic polyimide resins having excellent solubilityand heat resistance. These acid dianhydrides are particularly preferredbecause they can produce thermoplastic polyimide resins having asuitable glass transition temperature and a good balance amongcharacteristics such as low water absorption, heat resistance such asresistance to thermal decomposition, and the like.

Furthermore, another acid dianhydride can be combined with thatrepresented by formula (3) in a range which does not impair theadvantage of the present invention. Specifically, known tetracarboxylicdianhydrides can be used. Examples of the tetracarboxylic dianhydridesinclude aromatic tetracarboxylic dianhydrides such as pyromelliticdianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride,3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride,1,4,5,8-naphthalenetetracarboxylic dianhydride,2,3,6,7-naphthalenetetracarboxylic dianhydride,3,3′,4,4′-dimethyldiphenylsilanetetracarboxylic dianhydride,3,3′,4,4′-tetraphenylsilanetetracarboxylic dianhydride,1,2,3,4-furantetracarboxylic dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenylpropane dianhydride,4,4′-hexafluoroisopropylidenediphthalic anhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride,2,3,3′,4′-biphneyltetracarboxylic dianhydride, and p-phenylenediphthalicanhydride; and 4,4′-hexafluoroisopropylidenediphthalic anhydride.

Next, the diamine component will be described. It is essential to usethe diamine component represented by formula (4):

(wherein Y represents —C(═O)—, —SO₂—, —O—, —S—, —(CH₂)_(b)—, —NHCO—,—C(CH₃)₂—, —C(CF₃)₂—, —C(═O)O—, or a single bond, and a and bindependently represent an integer of 0 to 5).

Diamines represented by formula (4) can be used alone or in combinationof two or more. In formula (3), a plurality of Y's between respectiverepeat units may be the same or different, and each benzene ring maycontain a hydrocarbon group such as a methyl group or an ethyl group, ora halogen group such as Br or Cl.

Furthermore, the diamine compounds represented by formula (4) preferablyhave amino groups at the meta position because they can producethermoplastic polyimide resins having higher solubility than thoseproduced from diamine compounds having amino groups at the paraposition.

By using a diamine compound having amino groups at the meta position,the effect of improving the solubility of the thermoplastic polyimideresin of the present invention can be expected. However, the content ofsuch a diamine compound is preferably 50 to 100 mol % and morepreferably 80 to 100 mol % relative to a total of diamine components.

Examples of the diamine compounds represented by formula (4) include4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,3,3′-diaminodiphenyl ether, 4,4′-diaminodiphenyl thioether,3,4′-diaminodiphenyl thioether, 3,3′-diaminodiphenyl thioether,3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone,3,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone,4,4′-diaminobenzanilide, 3,4′-diaminobenzanilide,3,3′-diaminobenzanilide, 4,4′-diaminobenzophenone,3,4′-diaminobenzophenone, 3,3′-diaminobenzophenone,bis[4-(3-aminophenoxy)phenyl]methane,bis[4-(4-aminophenoxy)phenyl]methane,1,1-bis[4-(3-aminophenoxy)phenyl]ethane,1,1-bis[4-(4-aminophenoxy)phenyl]ethane,1,2-bis[4-(3-aminophenoxy)phenyl]ethane,1,2-bis[4-(4-aminophenoxy)phenyl]ethane,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]butane,2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene,1,4′-bis(4-aminophenoxy)benzene, 4,4′-bis(4-aminophenoxy)biphenyl,bis[4-(3-aminophenoxy)phenyl]ketone,bis[4-(4-aminophenoxy)phenyl]ketone,bis[4-(3-aminophenoxy)phenyl]sulfide,bis[4-(4-aminophenoxy)phenyl]sulfide,bis[4-(3-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether,1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,1,3-bis[4-(3-aminophenoxy)benzoyl]benzene,4,4′-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether,4,4′-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone,bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone,1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, and1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene. Examples of thediamine compounds represented by formula (3) in which amino groups arepresent at the meta position include1,1-bis[4-(3-aminophenoxy)phenyl]ethane,1,2-bis[4-(3-aminophenoxy)phenyl]ethane,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]butane,2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene,bis[4-(3-aminophenoxy)phenyl]ketone,bis[4-(3-aminophenoxy)phenyl]sulfide,bis[4-(3-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]ether,1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, and4,4′-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether. Besides the diaminecompounds represented by formula (4), m-phenylenediamine,o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine,p-aminobenzylamine, and the like can be used.

Also, a reactive diamine represented by formula (5) can be preferablyused.

(wherein Z represents —C(═O)—, —SO₂—, —O—, —S—, —(CH₂)_(d)—, —NHCO—,—C(CH₃)₂—, —C(CF₃)₂—, —C(═O)O—, or a single bond, c and d independentlyrepresent an integer of 0 to 5, and X's each represent an independentfunctional group containing at least one functional group selected from—OH, —COOH, —OCN, and —CN).

The diamines represented by formula (4) can be used alone or incombination of two or more. In formula (5), a reactive functional groupbonded to each benzene ring is an essential component, and a hydrocarbongroup such as a methyl group or an ethyl group, or a halogen group suchas Br or Cl may be further incorporated.

Examples of the diamines represented by formula (5) include3,3′-dihydroxy-4,4′-diaminobiphenyl and 3,5-diaminobenzoic acid. Forexample, the thermoplastic polyimide resin produced using3,3′-dihydroxy-4,4′-diaminobiphenyl contains hydroxyl groups, and thushas reactivity to an epoxy compound, a cyanate ester compound, or thelike serving as the thermosetting component. Therefore, in the polyimideresin composition containing the thermoplastic polyimide resin and thethermosetting component according to the present invention, crosslinkingproceeds to improve the heat resistance of the polyimide resincomposition. Since the use of an excess of reactive diamine may degradethe solubility of the resulting polyimide resin, the content of thereactive diamine is preferably 0 to 50 mol % and more preferably 0 to 20mol %.

For example, the hydroxyl groups in the thermoplastic polyimide resinproduced by reaction between the diamine component having an hydroxylgroup and the acid dianhydride may be converted to cyanate ester groupsby reaction with cyanogen bromide to produce a cyanate ester-modifiedpolyimide resin having reactivity.

The thermoplastic polyimide resin can be produced by dehydration andring closure of the corresponding polyamic acid polymer. The samesynthetic method for the polyamic acid and the same imidization methodas described above can be used.

The resulting thermoplastic polyimide resin has a relatively low glasstransition temperature. Thereby, in the present invention, in order thatthe resin composition has excellent processing properties, the glasstransition temperature of the thermoplastic polyimide resin ispreferably 350° C. or less, more preferably 320° C. or less, and mostpreferably 280° C. The lower limit of the glass transition temperatureis not particularly limited, but the lower limit is preferably 150° C.or more and more preferably 170° C. or more.

Next, the thermosetting component according to the present inventionwill be described. By adding an appropriate amount of the thermosettingcomponent to the thermoplastic polyimide resin, the surface of the metalfoil can be satisfactorily transferred in the process for laminating themetal foil, the laminate of the present invention, and the inner wiringboard. This causes the effect of improving adhesive strength to themicrocircuit formed by the semi-additive method. Thereto after curing,the transferred surface shape can be maintained in subsequent steps, andthereby the effect of maintaining adhesive strength to the microcircuitformed by the semi-additive method is increased. The thermosettingcomponent will be specifically described. Examples of the thermosettingcomponent include bismaleimide resins, bisallylnadiimide resins, phenolresins, cyanate ester resins, epoxy resins, acrylic resins, methacrylicresins, triazine resins, hydrosilyl curable resins, allyl curableresins, and unsaturated polyester resins or the like. These resins canbe used alone or in proper combination. Among these resins, epoxy resinsand cyanate ester resins are preferred because the well-balanced resincomposition can be produced.

In the present invention, any epoxy resin can be used. Usable examplesof the epoxy resins include bisphenol epoxy resins, halogenatedbisphenol epoxy resins, phenolic novolac epoxy resins, halogenatedphenolic novolac epoxy resins, alkylphenolic novolac epoxy resins,polyphenolic epoxy resins, polyglycol epoxy resins, alicyclic epoxyresins, cresol novolac epoxy resins, glycidylamine epoxy resins,urethane-modified epoxy resins, rubber-modified epoxy resins, andepoxy-modified polysiloxane or the like.

In the present invention, any cyanate ester resin can be used. Examplesof the cyanate ester resins include 2,2′-dicyanatodiphenylmethane,2,4′-dicyanatodiphenylmethane, 4,4′-dicyanatodiphenylmethane,bis(3-methyl-4-cyanatophenyl)methane,bis(3,5-dimethyl-4-cyanatophenyl)methane,bis(3,5-dibromo-4-cyanatophenyl)methane,bis(3,5-dichloro-4-cyanatophenyl)methane,2,2-bis(4-cyanatophenyl)propane,2,2-bis(3,5-dimethyl-4-cyanatophenyl)propane,2,2-bis(3-methyl-4-cyanatophenyl)propane, 4,4′-dicyanatodiphenyl ether,4,4′-dicyanatodiphenyl thioether,2,2-bis(4-cyanatophenyl)perfluoropropane,1,1-bis(4-cyanatophenyl)ethane,2,2-bis(3,5-dichloro-4-cyanatophenyl)propane, and2,2-bis(3,5-dibromo-4-cyanatophenyl)propane. Among these compounds,4,4′-dicyanatodiphenylmethane, 2,2-bis(4-cyanatophenyl)propane,bis(3,5-dimethyl-4-cyanatophenyl)methane, 4,4′-dicyanatodiphenylthioether, 2,2-bus(4-cyanatophenyl)perfluoropropane,1,1-bis(4-cyanatophenyl)ethane, and2,2-bis(3,5-dibromo-4-cyanatophenyl)propane are preferred, and4,4′-dicyanatodiphenylmethane, and2,2-bis(3,5-dibromo-4-cyanatophenyl)propane are more preferred.

Furthermore, a curing catalyst is preferably used, but the curingcatalyst need not necessarily be used. As the curing catalyst, animidazole, a tertiary amine, an organometallic compound, or the like canbe used. In particular, the organometallic compound is preferred, andfor example, cobalt octylate, zinc octylate, cobalt naphthenate, zincnaphthenate, or the like can be used. In addition, nonvolatile phenol ispreferably used for accelerating curing reaction. Examples of thenonvolatile phenol include bisphenols such as bisphenol A, bisphenol F,and bisphenol S; and nonylphenol.

The mixing ratio between the thermoplastic polyimide resin and thethermosetting component in the polyimide resin composition of thepresent invention is 100 parts by weight: 1 to 10,000 parts by weight,and more preferably 100 parts by weight: 5 to 2,000 parts by weight inthe weight of thermoplastic polyimide resin and the thermosettingcomponent each. With an excessively small amount of the thermosettingcomponent, the shape transferred from the metal foil cannot bemaintained, and thus the transferred shape cannot be maintained insubsequent steps, thereby failing to maintain the adhesive strength tothe microcircuit formed by the semi-additive method. In contrast, withan excessively large amount, the adhesive strength itself between thepolyimide resin composition layer and the microcircuit formed by thesemi-additive method may be degraded.

The inventors found that the polyimide resin composition containing thethermoplastic polyimide resin and the thermosetting component accordingto the present invention has high electrical insulation. Although thecircuit width and space width on a printed circuit board have decreasedmore and more, conventional materials have low insulation resistance andthus have difficulty in maintaining sufficient insulation. The polyimideresin composition of the present invention has high insulationresistance, and preferably has a volume resistivity of 5×10¹² Ω·cm ormore, and more preferably 1×10¹⁵ Ω·cm or more. The resistivity wasmeasured according to ASTM D-257. It was also found that the polyimideresin composition of the present invention has a low dielectric constantand a low dielectric loss tangent. As the clock frequency of asemiconductor increases, a wiring board material is required to have asmaller signal delay in the GHz band, a lower transmission loss, i.e., alower dielectric constant and a lower dielectric loss tangent. Therelative dielectric constant is preferably 3.5 or less, and thedielectric loss tangent is preferably 0.015 or less.

Next, the polymer film used in the laminate of the present inventionwill be described. In the present invention, the polyimide resincomposition layer comprising the thermoplastic polyimide resin and thethermosetting component is formed on the polymer film. Even when thepolyimide resin composition layer has a surface roughness Rz of 3 μm orless, the adhesive strength between the resin composition layer and themicrocircuit formed by the semi-additive method is sufficiently high.Also, since the microcircuit is not formed directly on the polymer filmof the present invention, adhesive force between the polymer film andthe microcircuit is not required. Furthermore, the polymer film of thepresent invention need not be passed directly through an expensiveprocess such as vapor deposition, sputtering, or the like. Furthermore,the laminate of the present invention comprises the polymer film withhigh rigidity, and thus the surface of the metal foil can besatisfactorily transferred even by lamination under low pressure.Therefore, the degree of freedom of lamination conditions can beincreased.

A material used for the polymer film of the present invention preferablyhas excellent dimensional stability, heat resistance, and mechanicalproperties. Examples of the polymer film include films of polyolefinssuch as polyethylene, polypropylene, and polybutene; ethylene-vinylalcohol copolymers; polystyrene; polyesters such as polyethyleneterephthalate, polybutylene terephthalate, and ethylene-2,6-naphthalate;nylon-6; nylon-11; aromatic polyamides; polyamide-imide resins;polycarbonates; polyvinyl chloride; polyvinylidene chloride; polyketoneresins; polysulfone resins; polyphenylenesulfide resins; polyetherimideresins; fluorocarbon resins; polyarylate resins; liquid crystal polymerresins; polyphenylene ether resins; and polyimide resins.

In the present invention, in order to impart sufficient rigidity to thelaminate, the polymer film preferably has a tensile modulus of 5 GPa ormore and more preferably 6 GPa or more.

Furthermore, since thermal stability is required in processing theprinted wiring board, the polymer film is required to have dimensionalstability. Therefore, the polymer film preferably has a coefficient oflinear expansion of 2.0×10⁻⁵/° C. or less, more preferably 1.5×10⁻⁵/° C.or less, and most preferably 1×10⁻⁵/° C. or less.

The polymer film is also required to have sufficient adhesive force tothe polyimide resin composition layer comprising the thermoplasticpolyimide resin and the thermosetting composition.

As the film satisfying the above-described properties, the same as thenon-thermoplastic polyimide resin film can be used.

Next, the adhesive layer constituting the laminate of the presentinvention will be described. The adhesive layer is laminated on the sideopposite to the layer comprising the polyimide resin composition.

Like in the above-described adhesive layer, adhesives for the adhesivelayer include the two types, i.e., a heat seal-type adhesive utilizing athermoplastic resin, and a curable adhesive utilizing curing reaction ofa thermosetting resin.

The laminate of the present invention comprises the polymer film and thelayer comprising the polyimide resin composition containing thethermoplastic polyimide resin and the thermosetting component, providedon one of the surfaces thereof. The laminate of the present inventionmay comprise the layers provided on both surfaces thereof, each of thelayers comprising the polyimide resin composition. In this case, thecompositions of the layers each comprising the polyimide resincomposition may be the same or different. The laminate of the presentinvention may comprise a layer comprising the polyimide resincomposition provided on one of the surfaces and an adhesive layerprovided on the other surface.

By using the polyimide resin composition, the laminate of the presentinvention is characterized in that the microcircuit formed by thesemi-additive method and the polyimide resin composition layer arestrongly bonded together even when the resin composition layer has asurface roughness Rz is 3 μm or less. Therefore, in view point of costan expensive process such as vapor deposition, sputtering, or the likeis not required.

Furthermore, a protective film may be provided on one or both of thesurfaces of the laminate of the present invention, for preventingcurling, surface contamination, flaw, and the like.

In lamination using the laminate of the present invention, a metal foilis used. The type of the metal foil is not particularly limited.Specifically, a copper foil, an aluminum foil, a nickel foil, or thelike is preferably used, but a copper foil generally used in manufactureof printed wiring boards is more preferred. After lamination, the metalfoil over the entire surface is etched to expose the surface of thepolyimide resin to which the surface of the metal foil is transferred.Then, the surface is subjected to chemical plating. As described above,in order to form the microcircuit with high adhesive strength, thesurface roughness Rz of the metal foil is preferably 3 μm or less andmore preferably 2 μm or less. The surface roughness Rz is preferablyabout 0.1 times or less the width of the circuit formed, for obtaining asatisfactory circuit shape.

The metal foil can be laminated by a method accompanied with heatingand/or pressing. Although hydraulic pressing, vacuum pressing, or vacuumlamination can be used, vacuum pressing or vacuum lamination ispreferred from the viewpoint of air-foaming and embedding property of aninner circuit. The maximum lamination temperature is 300° C. or less,preferably 250° C. or less, and more preferably 200° C. or less. Thelamination time is about 1 minute to 3 hours and preferably 1 minute to2 hours. In vacuum pressing or vacuum lamination, the pressure in achamber is 10 kPa or less and preferably 1 kPa or less. Since thelaminate of the present invention comprises the polymer film with highrigidity, the surface of the metal foil can be satisfactorilytransferred even by laminating under lower pressure, thereby increasingthe degree of freedom of lamination conditions. The lamination pressureis preferably 0.5 MPa or more and more preferably 0.7 MPa or more. Undera pressure of less than 0.5 MPa, the surface of the metal foil cannot besufficiently transferred, and thus adhesive strength to a chemicallyplated film may be decreased. After lamination, the resulting laminatecan be placed in a curing furnace such as a hot-air oven or the like. Inthis case, thermal curing reaction of the polyimide resin compositioncan be accelerated in the curing furnace. In particular, when thelamination time is decreased to, preferably, 20 minutes or less, use ofthe curing furnace is preferred from the viewpoint of improvedproductivity. For example, when the printed wiring board is produced bythe semi-additive method, the lamination time can be decreased to 20minutes or less in view of productivity. In this case, the metal foilover the entire surface can be removed before curing reaction of thepolyimide resin composition is completed, and then thermal curingreaction can be accelerated in the curing oven. This method permitscuring reaction in the curing furnace without foaming and is thuspreferred for a case in which the polyimide resin composition contains alarge amount of solvent residue.

Next, the process for removing the metal foil from the surface will bedescribed. The method for removing the metal foil from the surface isnot particularly limited, but etching is preferred. The metal foil ispreferably etched with an etchant selected according to the type of themetal foil. For a copper foil, an aluminum foil, a nickel foil, or thelike which can be preferably used as the metal foil, a generallyavailable ferric chloride etchant or cupric chloride etchant, or thelike is preferably used. Although the etching time and etchingtemperature are not particularly limited, the etching temperature ispreferably 10° C. or more in view of productivity. After the metal foilis removed from the surface, the laminate can be placed in a curingfurnace such as a hot-air oven or the like. As described above, in thiscase, curing reaction can be performed in the curing furnace withoutfoaming when the polyimide resin composition contains a large amount ofsolvent residue.

The polyimide resin composition layer in the laminate of the presentinvention may be in a semi-cured state or a cured state, or may besubjected to surface treatment for forming irregularity by a method suchas embossing, sand blasting, polishing, or the like. However, in theprocess for manufacturing the printed circuit board according to thepresent invention, the surface of the metal foil can be transferred tothe surface of the layer of the present invention by laminating thelaminate and the metal foil under heating and/or pressing, and thus thecircuit formed on the layer and the layer can be strongly bondedtogether. Therefore, the layer is preferably in a semi-cured state,particularly, without irregularity.

Any one of the laminates of the present invention comprises the polymerfilm and the polyimide resin composition layer formed thereon, the layercomprising the thermoplastic polyimide resin and the thermosettingcomponent. The polyimide resin composition layer in the laminate of thepresent invention is preferably as thin as possible for making use ofthe physical properties of the polymer film having excellentcharacteristics as a circuit substrate, such as low thermal expansion,heat resistance, electric characteristics, etc. The thickness of thepolyimide resin composition layer is preferably smaller than that of thepolymer film, more preferably ½ or less, and most preferably ⅕ or less,of that of the polymer film.

The laminate of the present invention can also be produced by a methodin which a polyimide resin composition solution, which is prepared bydissolving the polyimide resin composition containing the thermoplasticpolyimide resin and the thermosetting component in at least one solvent,is applied to the polymer film of the invention by a known generalcoating method such as die coating, knife coating, gravure coating, orthe like, and then dried at a temperature where curing reaction does notexcessively proceed. The solvent is not particularly limited as long asit dissolves the thermoplastic polyimide resin and the thermosettingcomponent. However, the type and amount of the solvent are preferablydetermined so as to suppress the amount of volatile residue in theformed polyimide resin composition layer to 10% by weight or less andmore preferably 7% by weight or less. In addition, the dryingtemperature and time must be appropriately set. With a volatile residueexceeding 10% by weight or more, foaming undesirably occurs in a heatingstep for manufacturing the printed circuit board or a solder reflow stepfor mounting a part on the manufactured printed circuit board. In viewof economics and workability, a low-boiling-point solvent having aboiling point of 160° C. or less is preferred. The solvent morepreferably has a boiling point of 130° C. or less and most preferably aboiling point of 105° C. or less. Preferred examples of such alow-boiling-point solvent include tetrahydrofuran (abbreviated to “THF”hereinafter, boiling point 66α C.), 1,4-dioxane (abbreviated to“dioxane” hereinafter, boiling point 103° C.), monoglyme (boiling point84° C.), dioxolane (boiling point 76° C.), and dimethoxyethane (boilingpoint 85° C.). These solvents can be used alone or in combination of twoor more.

In addition, the polyimide resin composition solution may be combinedwith an ordinary epoxy curing agent such as an acid anhydride, e.g., anacid dianhydride, an amine, imidazole, or the like, an accelerator, anyone of various coupling agents, according to the purposes for improvingwater absorption, heat resistance, adhesiveness, and the like.

In producing the laminate comprising the polyimide resin compositionlayers provided on both surfaces of the polymer film of the presentinvention, both layers can be formed as described above, and then driedat a temperature where curing reaction does not excessively proceed.Alternatively, one of the layers can be formed by the above-describedmethod, surface-treated, and cured, and then the other layer can beformed, followed by drying at a temperature where curing reaction doesnot excessively proceed. In this method, the compositions of thepolyimide resin composition layers may be the same or different. Inproducing the laminate comprising the polyimide resin composition layerformed on one surface and the adhesive layer formed on the othersurface, either of the polyimide resin composition layer and theadhesive layer may be first formed. However, it is important to takecare that the adhesive layer must be kept in a semi-cured state.

Furthermore, a sheet of the polyimide resin composition containing thethermoplastic polyimide resin and the thermosetting component can beformed and bonded to the polymer film. The lamination method is notlimited.

A resin film according to a third embodiment of the present inventionwill be described below.

Although the resin used for the resin film of the present invention isnot particularly limited, resins such as polyethylene terephthalate,polyethylene naphthalate, aromatic polyamide (aramid), polybenzoxazole,polyimide, and the like are preferred from the viewpoint of excellentheat resistance. Among these resins, polyimide resins are preferred fromthe viewpoint of an excellent balance between characteristics such aselectrical and mechanical properties. In particular, thermoplasticpolyimide resins having a glass transition temperature of 150° C. to300° C. are preferred from the viewpoint of easy formation of fineirregularity. With a glass transition temperature of less than 150° C.,the printed wiring board manufactured using the materials of the presentinvention tends to be degraded in heat resistance. With a glasstransition temperature of over 300° C., a high temperature is requiredfor forming fine irregularity, and thus processability tends todeteriorate.

The thermoplastic polyimide resin can be produced by a known method, forexample, the above-described imidization method.

As the acid dianhydride, the compounds represented by formula (3) can beused.

The polyimide resin is preferably produced using at least one diaminerepresented by formula (6):

(wherein Y represents —C(═O)—, —SO₂—, —O—, —S—, —(CH₂)_(m)—, —NHCO—,—C(CH₃)₂—, —C(CF₃)₂—, —C(═O)O—, or a single bond, R² representshydrogen, a halogen group, or an alkyl group having 1 to 4 carbon atoms,and m and r each represent an integer of 1 to 5). Thus the polyimideresin perform that the softening point (or glass transition temperature)can be easily controlled, and the polyimide resin having excellent heatresistance and low water absorption can be easily produced.

In order to improve properties such as adhesiveness, heat resistance,processability, and the like, the polyimide resin may be mixed withanother resin in a rang which causes no deterioration in the propertiessuch as heat resistance, low hygroscopicity, and the like. Examples ofthe other resins include thermosetting resins such as epoxy resins,cyanate ester resins, bismaleimide resins, bisallylnadiimide resins,phenol resins, acrylic resins, methacrylic resins, hydrosilyl curableresins, ally curable resins, and unsaturated polyester resins; andreactive side chain group-containing thermosetting polymers each havinga reactive group such as an allyl group, a vinyl group, an alkoxysilylgroup, or a hydrosilyl group at the side or end of the polymer chain.These resins may be used alone or in appropriate combination.

The resin film of the present invention has a surface shape on at leastone surface thereof, the surface shape having an arithmetic meanroughness Ra1 value of 0.05 μm to 1 μm measured with a cutoff value of0.002 mm, and a Ra1/Ra2 ratio of 0.4 to 1, Ra2 being a value measuredwith a cutoff value of 0.1 mm.

The arithmetic mean roughness Ra is defined in JIS B0601 (revised onFeb. 1, 1994). In the present invention, particularly, the value of thearithmetic mean roughness Ra is determined by observing the surface withan optical interference-type surface structure analyzer. In the presentinvention, the term “cutoff value” represents the wavelength determinedfor obtaining a roughness curve from a sectional curve (observed data)according to JIS B0601. Namely, the Ra value measured with a cutoffvalue of 0.002 mm means an arithmetic mean roughness calculated from aroughness curve, which is obtained by removing irregularity withwavelengths of 0.002 mm or more from the observed data. Therefore, whenthere is no irregularity with wavelengths of 0.002 mm or less, the Ravalue measured with the cutoff value of 0.002 mm is 0 μm.

A preferred example of the method for forming surface irregularity onthe resin is to partially remove the resin by sand blasting, polishing,or the like. When the resin has thermoplasticity, embossing can alsopreferably be used. In embossing, surface irregularity can be formed onthe resin by bringing the resin into contact with a metal materialhaving surface irregularity formed thereon at a temperature higher thanthe glass transition temperature (softening point) of the resin. Theembossing process is preferably accompanied with heating and pressing,and performed under conditions for forming proper irregularity. Anotherpreferred method is a replica method in which the roughened surface ofthe metal foil is brought into contact with the resin film, and thenheated and press-bonded thereto by pressing or the like at a temperaturehigher than the softening point of the resin, and then the metal foil ispeeled by a chemical method or a physical method such as peeling or thelike.

In a further method, a mixture of fine particles is mixed in the resinin production of the resin film.

In any one of the above-described methods, sand blasting, or polishingis preferably performed under conditions for forming appropriateirregularity.

In the present invention, any one of the above-described surfacetreatment methods such as “surface treatment for forming irregularity onthe surface of the thermoplastic polyimide resin”, “surface treatmentfor partially removing the surface layer of the thermoplastic polyimideresin”, and the like can be used as the surface treatment method.

In any one of the methods, it is important that the arithmetic meanroughness Ra1 value measured with a cutoff value of 0.002 mm is 0.05 μmto 1 μm, and the Ra1/Ra2 ratio to the Ra2 value measured with a cutoffvalue of 0.1 mm is controlled to 0.4 to 1. The Ra1 value is preferably0.1 μm to 0.8 μm and more preferably 0.2 μm to 0.6 μm, and the Ra1/Ra2ratio is 0.5 to 1 and more preferably 0.6 to 1. The Ra2 value indicatesirregularity with wavelengths of 100 μm or less. Since the irregularitywith wavelengths of over 100 μm possibly includes, at a high ratio,wrinkles and curls occurring in a film at the time of setting of asample for observing the surface shape, the Ra2 value is set as a valuesuitable for removing irregularity which is not original irregularity ofthe film. On the other hand, the Ra1 value indicates irregularity withwavelengths 2 μm or less. The inventors found that as the Ra1 valueincreases, wiring formability in forming micro-wiring with L/S of 30μm/30 μm or less and preferably 10 μm/10 μm or less tends to decrease.It was also found that irregularity with wavelengths of 2 μm or lesstends to have lower adhesiveness unless it has a certain height, i.e.,an arithmetic mean roughness value is 0.05 μm to 1 μm.

Namely, with a Ra1/Ra2 ratio of less than 0.4, the film has a largeamount of irregularity with wavelengths of 2 μm to 100 μm and thus hasdifficulty in forming a microcircuit. Also, with a Ra1/Ra2 ratio of lessthan 1 but close to 1, a film surface has a large amount ofmicro-irregularity with wavelengths of 2 μm or less and is thus suitablefor forming micro-wiring. Furthermore, with an Ra1 value of less than0.05 μm, the formed irregularity does not have a sufficient height andthus has lower adhesiveness, while with Ra1 value of over 1 μm, theformed irregularity has an excessively large height and thus hasdifficulty in forming a microcircuit.

In order to control the surface shape in the above-described range, itis important to form the surface shape under processing conditionssuitable for the resin film used.

For example, when the surface of the resin is partially dissolved with achemical, it is important to select the materials used for processing,such as the type and concentration of the chemical, a combination of aplurality of chemicals, and the like, and the processing conditions suchas chemical treatment temperature and treatment time, and the likeaccording to the resin film used. In particular, it is important tocombine the materials used for processing and the processing conditionsaccording to the characteristics of the resin film used.

When the resin film has thermoplasticity, micro-irregularity ispreferably formed by the embossing or replica method. In the replicamethod, it is important to appropriately select the materials used forprocessing, such as the type of the metal used (surface roughness,surface shape, and the like), and processing conditions such as thepressing temperature, pressure, time, and the like. In particular, it isimportant to combine the materials used for processing and theprocessing conditions according to the characteristics of thethermoplastic resin film used. When a surface with micro-irregularity isformed on the thermoplastic resin by the embossing or replica method, ametal roll with suitable irregularity and a copper foil are necessarilyused respectively. In order to form a suitable surface shape, it isimportant to properly determine the temperature and pressure duringpressing of the metal roll and metal foil on the thermoplastic material.

Specifically, the pressing temperature is in a range of glass transitiontemperatures of thermoplastic resins, i.e., −100° C. to 180° C., andpreferably −50° C. to 150° C., the linear pressure is in a range of 10kgf/cm to 200 kgf/cm and preferably 20 kgf/cm to 150 kgf/cm, and theprocessing velocity is in a range of 0.5 m/min to 5 m/min and preferably1 m/min to 3 m/min. It is important to determine suitable conditionsaccording to the characteristics (flowability in heating, the glasstransition temperature, and the elastic modulus in heating) of thethermoplastic resin material used.

The resin film used in the present invention may be a multi-layer resinfilm for compensating the characteristics of a resin film having aspecified surface, which has the properties such as the mechanicalproperties, heat resistance, processability, and the like. With respectto the multi-layer resin film, the polyimide resin is preferablycontained over the entirety of the layer from the viewpoint of anexcellent balance between characteristics such as insulating properties,thermal properties, mechanical properties, and the like.

In order to impart a lamination property to the adhesive layer, anotherresin layer can be formed on the surface opposite to the surface withthe surface shape according to the present invention, the layer having alower softening point or melting point than that of the resin with thesurface according to the present invention.

A method for forming a metal layer serving as a conductor layer on thespecified surface shape of the resin film according to the presentinvention is not particularly limited. Examples of the method includewet plating methods such as electroless plating and electroplating, anddry plating methods such as sputtering and vapor deposition.

The wet plating method is preferred from the viewpoint of cost.Alternatively, the metal foil may be bonded to the surface with anadhesive.

Examples of a method for forming an electronic circuit on the specifiedsurface shape on the resin film according to the present inventioninclude a method comprising forming a metal layer over the entiresurface and then partially etching the metal layer to form a circuit,and a method comprising forming a plating resist layer on the surface,performing exposure and development, and then laminating a metal layeron the exposed portions of the surface by plating to form a circuit.

Furthermore, a multilayer circuit board can be manufactured using theresin film of the present invention. In a method for manufacturing themultilayer circuit board, the resin film can be used for forming a resinlayer on the surface opposite to the surface having the specifiedsurface shape according to the present invention, the resin layer havinga lower softening point or melting point than that of the resin havingthe specified surface shape. Namely, the multilayer circuit board can bemanufactured by a method in which the resin layer having a lowersoftening point or melting point than that of the resin having thespecified surface shape is brought into contact with a substrate havinga circuit previously formed thereon, and then press-bonded together bypressing or lamination under heating and pressure, and then a circuit isformed on the surface having the specified surface shape.

Next, the method for manufacturing the printed circuit board will bedescribed.

Description will be made of the method for manufacturing the printedcircuit board using the laminate of the present invention, i.e., thetwo-layer structure laminate comprising the resin film and thenon-thermoplastic polyimide film or the polymer film; or the three-layerstructure laminate comprising the resin film/the non-thermoplasticpolyimide film or the polymer film/and the thermoplastic polyimide resinor the resin film, the resin film/the non-thermoplastic polyimide filmor the polymer film/and the copper foil, or the resin film/thenon-thermoplastic polyimide film or the polymer film, and the adhesivelayer. However, the present invention is not limited to this method, andcombination with another technical process can be made. The term “resinfilm” means a layer or film comprising the material containing thethermoplastic polyimide resin according to any one of the first to thirdembodiments as described above, or a layer comprising the resin film orthe polyimide resin composition containing the thermoplastic polyimideresin as described above and the thermosetting component. The resin filmmay be either surface-treated or surface-untreated.

Next, description will be made of the method for manufacturing theprinted circuit board using the laminate comprising the thermoplasticpolyimide resin film or the resin film and the non-thermoplasticpolyimide resin or the polymer film. In a first method for manufacturingthe printed circuit board, electroless copper plating is performed onthe surface of the thermoplastic polyimide resin film. The electrolessplating can be performed by chemical plating using a palladium catalystor direct plating using palladium, carbon or the like. Furthermore, aresist film is formed on the electroless-plated copper, and thenpartially removed by exposure and etching to expose a portion where acircuit is to be formed. Next, the circuit is formed by electrolyticcopper pattern plating using the exposed portion of theelectroless-plated copper as a feeding electrode. Then, the resist filmis removed, and then the unnecessary portion of the electroless-platedcopper is etched off to complete the circuit. This method is referred toas the “semi-additive method”.

A second method for manufacturing the printed circuit board is performedas follows: First, an electroless-plated copper layer is formed on thesurface of the thermoplastic polyimide resin film by the same method asdescribed above. Next, electrolytic copper plating is performed, andthen a resist film is formed on the surface of the electroplated copperlayer. Then, the resist film is partially removed by exposure anddevelopment to resolve a portion where a circuit is not to be formed,and then the unnecessary portion of the metal layer is etched off toform the circuit. This method is referred to as the “subtractivemethod”.

Next, description will be made of use of the laminate comprising thethermoplastic polyimide resin film or the resin film, thenon-thermoplastic polyimide film or the polymer film, and thethermoplastic polyimide film or the resin film.

In a first method for manufacturing the printed circuit board, via holesare first formed in the laminate so as to pass through it. The via holesare formed by a drilling method using a carbon dioxide gas laser orUV-YAG laser, or a method such as punching or drilling. In order to formsmall via holes, a drilling method using a laser is preferably used.After the via holes are formed, a desmearing process is performed forremoving smears mainly composed of the polyimide decomposition productand thermally carbonized products, which are produced in the via holesand around the via holes. The desmearing process can be performed by aknown method, such as a wet process using a permanganate, or a dryprocess using plasma or the like. Any one of the laminates of thepresent invention has durability to the permanganate desmearing processwhich is widely used for manufacturing printed circuit boards, and isthus desirably used. Next, electroless copper plating is performed onthe surface of the thermoplastic polyimide resin film and in the viaholes. A circuit is formed by the above-described semi-additive method.

A second method for manufacturing the printed circuit board is performedas follows: First, via holes are formed in the laminate comprising thethermoplastic polyimide resin film or the resin film, thenon-thermoplastic polyimide film or the polymer film, and thethermoplastic polyimide resin film or the resin film so as to passthrough the laminate. Next, the desmearing process is performed asdescribed above, and then electroless-plated copper layers are formed onthe surface of the thermoplastic polyimide resin and in the via holes.Next, panel plating is performed by electrolytic copper plating toelectrically connect both surfaces of the laminate through the viaholes. Then, a circuit is formed by the same subtractive method asdescribed above.

Next, description will show the method for manufacturing the printedcircuit board using the laminate comprising the thermoplastic polyimideresin film or the resin film, the non-thermoplastic polyimide film orthe polymer film, and the copper foil.

In a first method for manufacturing the printed circuit board, via holesare formed to pass through the thermoplastic polyimide resin film andthe non-thermoplastic polyimide film and extend to the metal copper foiland/or pass through the metal copper foil. The via holes are formed by amethod using a carbon dioxide gas laser or UV-YAG laser or a method suchas punching or drilling. After the via holes are formed, the surface ofthe thermoplastic polyimide resin and the insides of the via holes aredesmeared, and then a circuit is formed by the same semi-additive methodas described above.

In a second method for manufacturing the printed circuit board, viaholes are formed to pass through the thermoplastic polyimide resin filmor the resin film and the non-thermoplastic polyimide film or thepolymer film and extend to the metal copper foil or pass through themetal copper foil. Next, desmearing and electroless copper plating areperformed by the same method as described above, and then electrolyticcopper plating is performed on the electroless-plated copper layer toelectrically connect both surfaces of the laminate through the viaholes. Then, a circuit is formed by the same subtractive method asdescribed above.

Next, description will be made of the method for manufacturing thewiring board using the laminate comprising the thermoplastic polyimideresin film or the resin film, the non-thermoplastic polyimide film orthe polymer film, and the adhesive layer.

In a first method for manufacturing the printed circuit board, thelaminate and the wiring board are laminated by a method under heatingand/or pressure so that the adhesive layer faces the circuit surface ofthe wiring board on which a circuit has been formed. Next, via holes areformed to pass through the surface-treated thermoplastic polyimide resinfilm and the non-thermoplastic polyimide film and extend to the circuitof the wiring board. The via holes are formed by a drilling method usinga carbon dioxide gas layer, a UV-YAG layer, a drilling machine, a dryplasma apparatus, a UV laser, an excimer laser, or the like. After thevia holes are formed, the desmearing process is preformed for removingthe smears mainly composed of the melted and decomposition products ofpolyimide and the thermally carbonized products, which are produced atleast in the via holes. Then, electroless copper plating is performedafter the via holes are formed, and a circuit is formed by thesemi-additive method.

A second method for manufacturing the printed circuit board is performedas follows: First, the laminate and the wiring board are laminated by amethod under heating and/or pressure so that the adhesive layer facesthe circuit surface of the wiring board on which a circuit has beenformed. Next, via holes are formed to pass through the thermoplasticpolyimide resin film or the resin film and the non-thermoplasticpolyimide film or the polymer film and extend to the circuit of thewiring board. After the via holes are formed, the desmearing process andelectroless copper plating are performed by the same method as describedabove, and then, a circuit is formed by the subtractive method.

In these methods, the metal layer can be formed by sputtering instead ofelectroless plating. In manufacturing the multilayer printed wiringboard, the resin film of the present invention may be laminated on the aflexible printed wiring board comprising a resin film such as apolyimide film or the like used as a base, on a surface of which acircuit has been formed, or a rigid board comprising a glass epoxysubstrate, a bismaleimide-triazine substrate, or the like, using athermoplastic or thermosetting adhesive so that the surface having thespecified surface shape faces outward. Then, a circuit may be formed onthe resin film by the same method as any one of the above-describedmethods for manufacturing the printed circuit board.

Any of the laminates of the present invention has durability to thedesmearing process using a general permanganate in the process formanufacturing the printed circuit board, and thus can be desirably used.Also, electroless plating can be performed by chemical plating using thecatalytic function of a noble metal such as palladium or the like, andcopper, nickel, gold, or the like can be used as the deposited metal.Alternatively, direct plating using palladium, carbon, an organicmanganese conductive film, or a conductive polymer can be performed, anda liquid resist, a dry film resist, or the like can be used as theresist. In particular, the dry film resist can be preferably usedbecause of its excellent handleability. When a circuit is formed by thesemi-additive process, etching for removing the feeding layer isappropriately selected according to the type of the electroless platingperformed in the process. For example, in electroless copper plating, asulfuric acid/hydrogen peroxide or ammonium persulfate/sulfuric acidetchant is preferably used. In electroless nickel or gold plating or thelike, an etchant which can selectively etch such a metal is preferablyused. Furthermore, the via holes are preferably formed with a UV-YAGlaser or excimer laser for forming small via holes, particularly viaholes of 50 μm or less in diameter, preferably via holes of 30 μm orless in diameter.

In the present invention, chemical etching can be performed by any oneof many known methods, for example, electroless copper plating, solderelectroplating, tin electroplating, electroless nickel plating,electroless gold plating, electroless silver plating, electroless tinplating, or the like. However, in industrial viewpoint and the viewpointof electrical properties such as migration resistance, and the like,electroless copper plating and electroless nickel plating are preferred,and electroless copper plating is particularly preferred.

When the laminate of the present invention comprises the polymer filmand the layer provided on one surface thereof, the layer comprising thepolyimide resin composition containing the thermoplastic polyimide resinand the thermosetting component, or comprises the polymer film and thelayers provided on both surfaces thereof, each of the layers comprisingthe polyimide resin composition, the laminate and an inner wiring boardmust be strongly bonded together with an adhesive. As the adhesive, anordinary adhesive can be used, and the same adhesive as those describedabove can be preferably used.

As the adhesive used for laminating the laminate of the presentinvention and the inner wiring board, a polyimide resin, an epoxy resin,or a cyanate ester resin, or a blend thereof can be preferably used fromthe viewpoint of adhesiveness, processability, heat resistance,flexibility, dimensional stability, low dielectric properties, cost,etc. Although the thickness of the adhesive layer is not particularlylimited, the thickness is preferably sufficient to bury the circuit ofthe inner wiring board therein. Also, the form of the adhesive is notparticularly limited, but a sheet is preferred in view of handleability.

In the laminate of the present invention comprising the polymer film andthe layers provided on both surfaces thereof according to the presentinvention, the layers each comprising the polyimide resin composition,the polyimide resin composition layer and the adhesive must be stronglybonded together, and thus a care must be taken to select the adhesive.In the laminate, either of the polyimide resin composition layers may bebonded to the adhesive, and the thickness of the polyimide resincomposition layer bonded to the adhesive is not particularly limited. Inaddition, surface treatment can be performed for strongly bonding thelayer and the adhesive together. On the other hand, in the method formanufacturing the printed circuit board of the present invention, thesurface of the metal foil can be transferred to the layer surface bylaminating the laminate of the present invention and the metal foilunder heating and/or pressure, and thus the circuit formed on the layercan be strongly bonded to the layer. Therefore, in the laminate, thepolyimide resin composition layer laminated in contact with the metallayer is preferably in the semi-cured state, particularly, withoutirregularity.

The laminate produced as described above in the present inventionenables the formation of a microcircuit having high insulationresistance and high adhesive strength, and thus can be used as amaterial for printed wiring boards having micro-wiring and a materialfor build-up wiring boards.

In the method for manufacturing the printed circuit board of the presentinvention, the chemical plating must be preformed to a thicknesssufficient to form a plated film serving as the feeding electrode in thevia holes and/or through holes formed by laser drilling or the like.Therefore, the thickness is preferably 100 nm to 1,000 nm and morepreferably 200 nm to 800 nm. With a thickness of less than 100 nm, thethickness of the electroplated film serving as the feeding electrodevaries, while with a thickness of over 1,000 nm, extra etching must beperformed in the etching step in the method for manufacturing theprinted circuit board of the present invention, thereby decreasing thecircuit thickness or the circuit width to be smaller than a circuitdesign value. Furthermore, undercutting occurs to cause the problem ofimpairing the circuit shape.

In the method for manufacturing the printed circuit board of the presentinvention, known materials widely commercially available asphotosensitive plating resist can be used. In the manufacturing method,a photosensitive plating resist having a pitch resolution of 50 μm orless is preferably used for decreasing the pitch. Of course, the printedwiring board obtained by the manufacturing method of the presentinvention may include a circuit with a wiring pitch of 50 μm or less anda circuit with a pitch larger than this.

In the method for manufacturing the printed circuit board of the presentinvention, the chemically plated layer can be removed with a known quicketchant. Preferred examples of such etchant include a sulfuricacid-hydrogen peroxide etchant, an ammonium persulfate etchant, a sodiumpersulfate etchant, a diluted ferric chloride etchant, and a dilutedcupric chloride etchant.

The resin film used in the present invention may further contain acomponent other than the above-described components as long as thecharacteristics are not degraded. Similarly, the resin film of thepresent invention may be subjected a step other than the above-describedsteps.

As a result of research, the inventors found that the polyimide resincomposition layer according to the present invention can be stronglybonded to the chemically plated film even when the surface roughness is3 μm or less. Namely, high adhesiveness and formation of a microcircuitcan be simultaneously satisfied. Furthermore, when the surface roughnessis low, the feeding electrode can be removed by etching within a shorttime in the semi-additive method, as compared with the case of highsurface roughness. Therefore, the resin composition layer is suitablefor forming a microcircuit. In other words, etching can be completedwithin a short time to decrease the amount of etching of the circuitpattern formed by electroplating, thereby permitting the formation of acircuit according the design width and thickness as desirable.Therefore, the composition layer is particularly preferred for forming amicrocircuit.

Furthermore, by using the laminate of the present invention, ordinaryprocesses such as the desmearing process and electroless plating processcan be applied, and thus a high-density circuit with a L/S of 20 μm/20μm or less, particularly 10 μm/10 μm or less, can be formed. Therefore,the printed circuit board having excellent adhesiveness and highadhesive reliability in a severe environment of high temperature andhigh humidity, and the like can be obtained. Furthermore, the laminateof the present invention permits the manufacture of a flexible printedcircuit board with excellent adhesiveness and environmental stability, amultilayer flexible printed wiring board comprising a laminate offlexible printed wiring boards, a rigid-flex wiring board comprising alaminate of a flexible printed wiring board and a rigid printed wiringboard, a build-up wiring board, a TAB tape, a COF substrate comprising asemiconductor element mounted on directly on a printed circuit board, aMCM substrate, and the like.

In the method for manufacturing the printed circuit board of the presentinvention, a microcircuit pattern can be satisfactorily formed on thesurface micro-irregularity of the polyimide resin composition layer ofthe present invention even under lamination conditions such as arelatively low pressure, and high adhesive strength can be achieved.Also, the feeding electrode on the surface micro-irregularity can besufficiently etched off without residue, and the polyimide resincomposition of the present invention has high insulating resistance. Forthese two reasons, high insulation property required for a microcircuitspace, which will contain the further narrowed pitch in future, can berealized. Furthermore, the laminates of the present invention can bepreferably used for the printed circuit board and the method formanufacturing the printed circuit board according to the presentinvention.

Although the advantages of the present invention will be described infurther detail below with reference to examples, the present inventionis not limited to these examples, and various modifications, changes,and alternations can be made by a person skilled in the art within thescope of the present invention. In the examples below, formation ofvarious non-thermoplastic polyimide films, formation of thermoplasticpolyimide resins, formation of laminates, synthesis and formation ofadhesive layers, lamination, electroless plating, and variousmeasurements and evaluations were carried out as described below.

<Preparation A of Non-Thermoplastic Polyimide Film>

A conversion agent comprising 17 g of acetic anhydride and 2 g ofisoquinoline was mixed with 90 g of a DMF (N,N-dimethylformamide)solution of 17% by weight polyamic acid synthesized from pyromelliticdianhydride, 4,4′-diaminodiphenyl ether, and p-phenylenediamine at amolar ratio of 4/3/1, followed by stirring. After defoaming bycentrifugation, the resultant mixture was applied by casting to athickness of 700 μm on an aluminum foil. The process from stirring todefoaming was performed under cooling at 0° C. The resulting laminate ofthe aluminum foil and the polyamic acid solution layer was heated at110° C. for 4 minutes to form a self-supporting gel film. The gel filmhad a volatile residue content of 30% by weight and a rate ofimidization of 90%. Then, the gel film was peeled from the aluminum foiland fixed to a frame. The gel film was heated at 300° C., 400° C., and500° C. for 1 minute each to produce a polyimide film A having athickness of 25 μm.

<Preparation B of Non-Thermoplastic Polyimide Film>

A polyimide film B was formed by the same method as Formation A exceptthat polyamic acid was synthesized from pyromellitic dianhydride and4,4′-diaminodiphenyl ether at a molar ratio of 1/1.

<Preparation C of Non-Thermoplastic Polyimide Film>

A polyimide film C was formed by the same method as Formation A exceptthat a DMAc (N,N-dimethylacetamide) solution of 17% by weight polyamicacid was used, the polyamic acid being synthesized from3,3′,4,4′-biphenyltetracarboxylic dianhydride,p-phenylenebis(trimellitic acid monoester anhydride),p-phenylenediamine, and 4,4′-diaminodiphenyl ether at a molar ratio of4/5/7/2.

<Preparation X of Thermoplastic Polyimide Precursor>

In DMF, 1,2-bis[2-(4-aminophenoxy)ethoxy]ethane (referred to as “DA3EG”hereinafter) and 2,2′-bis[4-(4-aminophenoxy)phenyl]propane (referred toas “BAPP” hereinafter) at a molar ratio of 3:7 were dissolved, and3,3′,4,4′-ethylene glycol dibenzoate tetracarboxylic dianhydride(referred to as “TMEG” hereinafter) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (referred to as “BTDA” hereinafter) at amolar ratio of 5:1 were added to the resultant solution under stirring.The resultant mixture was stirred for about 1 hour to obtain a polyamicacid DMF solution having a solid content of 20% by weight. Then, asingle sheet of the resulting thermoplastic polyimide resin was formed,and the glass transition temperature of the sheet was measured. As aresult, the glass transition temperature was 152° C.

<Preparation Y of Thermoplastic Polyimide Precursor>

BAPP was uniformly dissolved in DMF, and3,3′,4,4′-biphenyltetracarboxylic dianhydride andethylenebis(trimellitic acid monoester anhydride) at a molar ratio 4:1were added to the resultant solution under stirring so that the aciddianhydride and the diamine became equimolar. Then, the resultantmixture was stirred for about 1 hour to obtain a polyamic acid DMFsolution having a solid content of 20% by weight. Then, a single sheetof the resulting thermoplastic polyimide resin was formed, and the glasstransition temperature of the sheet was measured. As a result, the glasstransition temperature was 225° C.

<Preparation Z of Thermoplastic Polyimide Precursor>

In DMF, 1,3-bis(3-aminophenoxy)benzene and 3,3′-dihydroxybenzidine at amolar ratio of 4:1 were dissolved, and4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) was added tothe resultant solution under stirring so that the acid dianhydride andthe diamine became equimolar. Then, the resultant mixture was stirredfor about 1 hour to obtain a polyamic acid DMF solution having a solidcontent of 20% by weight. Then, a single sheet of the resultingthermoplastic polyimide resin was formed, and the glass transitiontemperature of the sheet was measured. As a result, the glass transitiontemperature was 160° C.

<Formation of Laminate>

Each of the above-described non-thermoplastic polyimide films A to Cformed in Preparations A to C, respectively, was used as a core film,and each of the DMF solutions of polyamic acid, which was a precursor ofthermoplastic polyimide, prepared in Preparations X, Y, and Z wasapplied to both or one of the surfaces of the core film by a gravurecoater.

After application, heat treatment was performed to remove the solvent orimidize the polyamic acid at a final heating temperature of 390° C. toform a laminated polyimide film comprising a non-thermoplastic polyimidelayer and a thermoplastic polyimide layer. The amount of coating waschanged to form films comprising thermoplastic polyimide layers withdifferent thicknesses. For example, when the non-thermoplastic polyimidefilm A was used, the resulting film comprising the thermoplasticpolyimide layer formed on one surface by using the precursor prepared byPreparation X is denoted by X/A, the resulting film comprising thethermoplastic polyimide layers formed on both surfaces by using theprecursor prepared by Preparation X is denoted by X/A/X, and theresulting film comprising the thermoplastic polyimide layer formed onone surface by using the precursor prepared by Preparation X, and acopper foil formed on the other surface is denoted by X/A/Cu.

<Synthesis and Formation of Adhesive Layer>

In a nitrogen atmosphere, one equivalent ofbis{4-(3-aminophenoxy)phenyl}sulfone (referred to as “BAPS-M”hereinafter) was dissolved in N,N-dimethylformamide (referred to as“DMF” hereinafter). The resultant solution was stirred under cooling,and one equivalent of 4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalicanhydride) (referred to as “BPADA” hereinafter) was added to thesolution to obtain a polyamic acid polymer solution having a solidcontent of 30% by weight. The polyamic acid solution was heated at 200°C. for 180 minutes under a reduced pressure of 665 Pa to obtain a solidthermoplastic polyimide resin. The resultant polyimide resin, a novolacepoxy resin (Epicoat 1032H60: manufactured by Yuka-Shell Company), and4,4′-diaminodiphenylsulfone (referred to as “4,4′-DDS” hereinafter) weremixed at a weight ratio of 70/30/9. Then, the resultant mixture wasdissolved in dioxolan so that the solid content was 20% by weight, toobtain an adhesive solution. The resulting adhesive solution was appliedto the polyimide film surface of the laminate formed as described aboveso that the dry thickness was 12.5 μm, and then dried at 170° C. for 2minutes to obtain a laminate.

<Lamination Process>

An inner circuit board was formed using a glass epoxy copper-cladlaminate comprising a copper foil of 12 μm in thickness. Then, thelaminate formed as described above was laminated on the inner circuitboard and cured by vacuum pressing under conditions including atemperature of 200° C., a heat plate pressure of 3 MPa, a pressing timeof 2 hours, and a vacuum condition of 1 kpa.

<Electroless Copper Plaiting>

An electroless plating process manufactured by Atotech K. K. shown inthe table below was used.

(Electroless Plating Conditions)

TABLE 1 Process Composition of Reactive Solution Condition CleanerCleaner Securigant 902 (※) 40 ml/l 60° C. Conditioner Cleaner Additive902 (※) 3 ml/l 5 min. Sodium Hydroxide 20 g/l dipping (Washing) PredipPredip Neogant B (※) 20 ml/l room Sulfuric acid 1 ml/l temp. 1 min.dipping Adding Activater Neogant 834 conc (※) 40 ml/l 40° C. catalystSodium Hydroxide 4 g/l 5 min. Boric Acid 5 g/l dipping (Washing)Reduction Reducer Neogant (※) 1 g/l room Sodium Hydroxide 5 g/l(Washing) Elecroless Basic Solutin Printgant 80 ml/l 35° C. copperMSK-DK (※) 15 min. plating Copper Solution Printgant 40 ml/l dipping MSK(※) Stabilizer Printdgant 3 ml/l MSK-DK (※) Reducer Copper (※) 14 ml/l(Washing) (※) (manufactured by Atotech K. K.)<Copper Electroplating Method>

Copper electroplating was performed by pre-washing in 10% sulfuric acidfor 30 seconds and then plating at room temperature for 40 minutes. Thecurrent density was 2 A/dm².

<Formation of Resist Layer>

A liquid photosensitive plating resist (manufactured by Japan SyntheticRubber Co., Ltd., THB320P) was coated and then exposed to light with ahigh-voltage mercury-vapor lamp through a mask to form a resist patternhaving desired L/S.

<Measurement of Adhesive Strength>

Adhesive strength was measured with a pattern width of 3 mm, a peelingangle of 90°, and a peeling rate of 50 mm/min according toIPC-TM-650-method.2.4.9.

<Pressure Cooker Test>

The test was performed at 121° C. and 100% RH for 96 hours.

<Measurement of Surface Roughness>

The ten-point medium height on a thermoplastic polyimide resin surfacewas measured with an optical interference-type surface roughness meter,New View 5030 System, manufactured by ZYGO Corporation.

<Measurement of Surface Shape>

The arithmetic mean roughness on a resin surface was measured with anoptical interference-type surface roughness meter, New View 5030 System,manufactured by ZYGO Corporation under the following conditions:

(Measurement Conditions)

Objective lens: ×50 Miura Image Zoom: 2

FDA Res: Normal

(Analytical Conditions)

Remove: Cylinder

Filter: High Pass

Filter Low Waven: 0.002 mm and 0.1 mm

<Confirmation of Metal Etching Residue in Micro-Wiring>

The spaces of wiring were observed with SEMEDX Type-N (manufactured byHitachi, Ltd.) to confirm the presence of a peak of a metal element.

<Measurement of Adhesive Strength>

Adhesive strength was measured with a pattern width of 3 mm, a peelingangle of 90°, and a peeling rate of 50 mm/min according toIPC-TM-650-method.2.4.9.

<Measurement of Coefficient of Linear Expansion>

The coefficient of linear expansion of a thermoplasticpolyimide/non-thermoplastic polyimide laminate was measured with TMA120Cmanufactured by Seiko Instruments Inc. under the conditions including aheating rate of 20° C./min, a nitrogen flow rate of 50 ml/min, a sampleshape of 3 mm in width and 10 mm in length, and a load of 3 g. Themeasurement was conducted two times from room temperature to 300° C.,and the average from 100° C. to 200° C. in the second measurement wasdetermined as the coefficient of linear expansion of the laminate.

<Glass Transition Temperature>

The storage modulus (ε′) of a cured resin sheet was measured withDMS-200 (manufactured by Seiko Instruments Inc.) with a measurementlength (measurement jig distance) of 20 mm under the conditions below.The inflection point of the storage modulus (ε′) curve was determined asthe glass transition temperature (° C.) of the resin.

Measurement atmosphere: dry air atmosphere

Measurement temperature: 20 to 400° C.

Measurement sample: cured resin sheet of 9 mm in width and 40 mm inlength

EXAMPLES 1 TO 9

Each of the polyamic acid solutions prepared in Preparations X, Y, and Zwas applied to one of the surfaces of each of the non-thermoplasticpolyimide films A, B, and C of 25 μm in thickness formed in PreparationsA, B, and C to form a laminate. The thickness of the thermoplasticpolyimide layer was 3 μm, and a copper foil was placed on thethermoplastic polyimide layer and then laminated with a heat roll at atemperature of 340° C., a linear pressure of 20 kgf/cm, and a linearvelocity 1.5 m/min. As the copper foil, a rolled copper foil, BHY-22B-T,of 18 μm in thickness (Rz=1.5 μm) manufactured by Japan Energy Co., Ltd.was used. Then, the laminated copper foil was completely removed using ahydrochloric acid/ferric chloride etchant to obtain a laminatecomprising a surface-treated thermoplastic polyimide resin filmaccording to the present invention. The surface roughness of thesurface-treated film was measured.

Then, electroless copper plating and electrolytic copper plating wereperformed to form a copper layer having a thickness of 18 μm, andadhesive strength was measured at room temperature and after thepressure cooker test. The results are shown in Table 2.

COMPARATIVE EXAMPLES 1 TO 3

A laminate was formed by the same method as in Examples 1 to 9 exceptthat surface treatment comprising laminating the copper foil and thenremoving was not conducted, and the same test as in Example 1 wasconducted. The results are shown in Table 2.

TABLE 2 Adhesive Surface Strength Roughness Adhesive after PCT MaterialSurface- Rz Ra1 Ra2 Ra1/ strength test Example Composition treatment(μm) (μm) (μm) Ra2 (N/cm) (N/cm) 1 X/A Rolled 1.1 0.19 0.23 0.83 9 7Copper Fiol 2 X/B Rolled 1.1 0.18 0.22 0.82 9 7 Copper Fiol 3 X/C Rolled1.3 0.21 0.27 0.78 9 6 Copper Fiol 4 Y/A Rolled 1.2 0.17 0.25 0.68 8 6Copper Fiol 5 Y/B Rolled 1.1 0.15 0.25 0.60 10 6 Copper Fiol 6 Y/CRolled 1.3 0.18 0.28 0.64 8 7 Copper Fiol 7 Z/A Rolled 1.2 0.19 0.210.90 9 7 Copper Fiol 8 Z/B Rolled 1.1 0.18 0.21 0.86 10 6 Copper Fiol 9Z/C Rolled 1.1 0.18 0.20 0.90 9 7 Copper Fiol Comparative X/A none 0.10.02 0.03 0.67 <1 <1 Example 1 Comparative Y/A none 0.1 0.02 0.03 0.67<1 <1 Example 2 Comparative Z/A none 0.1 0.02 0.02 1 <1 <1 Example 3

The results indicate that in the laminate of the present invention, anelectroless-plated layer with a high adhesiveness of 5 N/cm or more canbe formed on a moderately roughened surface with low roughness.

EXAMPLES 10 TO 26

Experiment was carried out to confirm the effects of various surfacetreatments. The polyamic acid solution prepared in Preparation Y wasapplied to one of the surfaces of the non-thermoplastic polyimide filmof 25 μm in thickness formed in Preparation B to form a laminate. Thethickness of the thermoplastic polyimide layer was each of 1, 3, and 5μm.

(1) Surface treatment with an electrolytic copper foil was performed bylaminating an electrolytic copper foil, 3EC-VLP oil (thickness 18 μm,Rz=4.6 μm) manufactured by Mitsui Kinzoku K. K. by the same method as inExamples 1 to 9.

(2) Surface treatment with a permanganate was performed by thepermanganate desmearing system (manufactured by Atotech K. K.) shown inthe table below.

<Conditions of Permanganate Desmearing>

TABLE 3 process Composition of Reactive Solution condition SwellingSwelling Securigant P (※) 500 ml/L 60° C. NaOH 3 g/l 5 min. dipping(Washing) Micro- Concentrate Compact CP (※) 550 ml/L 80° C. etching NaOH40 g/l 5 min. dipping (Washing) Redution Reduction Solution Securigant70 ml/L 40° C. P500 (※) 5 min. Sulfuric Acid 50 ml/l dipping (Washing)(※) (manufactured by Atotech K. K.)

(3) Surface treatment with an organic alkali compound was performed bydipping the laminate in a mixed solution of potassium hydroxide,ethanolamine, and water at a weight ratio of 2/5/1 at 30° C. for 5minutes, and then sufficiently washing the laminate with water.

(4) Surface treatment with an organic solvent is performed by dippingthe laminate in DMF used as a solvent at 40° C. for 5 minutes and thensufficiently washing the laminate with water.

These surface-treated laminates were evaluated by the same method as inExamples 1 to 9. When two types of surface treatments were combined, thesurface treatments were sequentially performed in the order shown inTable 4 (in which “rolled copper foil+permanganate” means that surfacetreatment with a rolled copper foil was performed first, and treatmentwith a permanganate was performed next). The results are shown in Table4.

COMPARATIVE EXAMPLE 4

The same evaluation as described above was performed except that thelaminate used Examples 10 to 26 was not subjected to surface treatment.The results are shown in Table 4.

COMPARATIVE EXAMPLE 5

For comparison, the same evaluation as described above was performedusing an epoxy resin. First, 80 parts of EP-1001 manufactured byYuka-Shell Epoxy Co., Ltd., 10 parts of EP-828 manufactured byYuka-Shell Epoxy Co., Ltd., 10 parts of EP-154 manufactured byYuka-Shell Epoxy Co., Ltd., 0.4 part of imidazole curing accelerator2E4MZ manufactured by Shikoku Kasei Co., Ltd., and 3.5 parts ofdicyandiamide were uniformly mixed and/or dispersed. Then, the resultantmixture was dissolved in methyl ethyl ketone, and the resulting solutionwas applied to a uniform thickness on a glass epoxy substrate, and thendried and cured at 120° C. for 15 minutes and at 150° C. for 30 minutesto obtain an epoxy resin film. Then, the same desmearing process as inExamples 1 to 9 was performed, and surface roughness was evaluated.Next, electroless plating and electroplating were performed by the sameoperation as in Examples 1 to 9, and adhesive strength was evaluated.

TABLE 4 Thickness of Adhesive Thermoplastic Surface Strength MaterialPolyimide Roughness Adhesive after PCT Composition layer Surface- Rz Ra1Ra2 Ra1/ strength test Example B = 25 μm (μm) treatment (μm) (μm) (μm)Ra2 (N/cm) (N/cm) 10 Y/B 1 Rolled 0.7 0.12 0.19 0.63 5 4 Copper Fiol 11Y/B 5 Rolled 1.2 0.17 0.25 0.68 9 6 Copper Fiol 12 Y/B 1 Electrolytic0.7 0.13 0.23 0.57 5 3 Copper Foil 13 Y/B 3 Electrolytic 3.5 0.21 0.510.41 11 6 Copper Foil 14 Y/B 5 Electrolytic 3.7 0.22 0.55 0.40 11 6Copper Foil 15 Y/B 1 Permanganate 0.2 0.06 0.07 0.86 6 4 16 Y/B 3Permanganate 0.2 0.06 0.07 0.86 5 4 17 Y/B 5 Permanganate 0.2 0.06 0.080.75 6 4 18 Y/B 1 Ethanolamine 0.1 0.05 0.05 1.00 5 4 19 Y/B 3Ethanolamine 0.1 0.05 0.06 0.83 5 4 20 Y/B 5 Ethanolamine 0.2 0.06 0.061.00 6 5 21 Y/B 1 DMF 0.3 0.07 0.09 0.78 5 4 22 Y/B 3 DMF 0.3 0.06 0.090.67 6 4 23 Y/B 5 DMF 0.3 0.06 0.08 0.75 5 4 24 Y/B 1 Rolled Copper 0.80.14 0.22 0.64 6 4 Fiol + Permanganate 25 Y/B 3 Rolled Copper 1.5 0.180.29 0.62 8 5 Fiol + Permanganate 26 Y/B 5 Rolled Copper 1.6 0.19 0.290.66 8 5 Fiol + Permanganate Comparative Y/B none 0.1 0.02 0.03 0.67 <1<1 Example 4 Comparative Epoxy — Permanganate 0.8 0.06 0.16 0.38 3 <1Example 5 Resin

Table 4 indicates that the thickness of a proper thermoplastic polyimideresin film depends upon the treatment type, and, in order to exhibithigh adhesiveness, the thickness of the thermoplastic polyimide resinfilm is preferably larger than the surface roughness Rz of the roughenedsurface of the thermoplastic polyimide resin subjected to surfacetreatment, and more preferably at least 2 times the surface roughnessRz. It is also found that the thermoplastic polyimide resin of thepresent invention has higher adhesiveness than that of an epoxy resinwith the same degree of surface roughness.

EXAMPLES 27 TO 38

The polyamic acid solution prepared in Preparation Y was applied to bothsurfaces of each of the non-thermoplastic polyimide films of 7.5 μm,12.5 μm, 25 μm, and 50 μm, respectively, in thickness formed inPreparation C of polyimide film to form laminates comprisingthermoplastic polyimide layers having different thicknesses. Each of thethermoplastic polyimide layers was surface-treated using the same copperfoil as in Examples 1 to 9, and the coefficient of thermal expansion wasmeasured. Then, electroless plating and electrolytic plating wereperformed by the same method as in Examples 1 to 9 to form a copperlayer having a thickness of 18 μm, and adhesive strength was measured atroom temperature and after the pressure cooker test. The results areshown in Table 5. In experiment, the coefficient of thermal expansion ofthe non-thermoplastic film C was 12 ppm/° C. The coefficient of thermalexpansion was measured after formation of the thermoplastic layer, andevaluated on the basis of the following criteria: A thermal expansioncoefficient of 20 ppm/° C. or less was evaluated as A, a thermalexpansion coefficient of 25 ppm/° C. or less was evaluated as B, athermal expansion coefficient of 30 ppm/° C. or less was evaluated as C,and a thermal expansion coefficient of 30 ppm/° C. or more was evaluatedas D.

TABLE 5 Thickness Thickness Adhesive Of Non- of Surface StrengthCoefficient thermoplastic Thermoplastic Roughness Adhesive after Ofpolyimide Film C Polyimide layerY Rz Ra1 Ra2 Ra1/ strength PCT testLinear Example (μm) (μm) (μm) (μm) (μm) Ra2 (N/cm) (N/cm) Expansion 277.5 1 0.7 0.12 0.18 0.67 5 4 A 28 7.5 3 1.1 0.15 0.24 0.63 8 6 C 29 7.55 1.2 0.17 0.25 0.68 9 6 D 30 12.5 1 0.6 0.12 0.17 0.71 6 4 A 31 12.5 31.2 0.17 0.26 0.65 8 5 B 32 12.5 5 1.2 0.17 0.27 0.63 8 6 C 33 25 1 0.60.12 0.18 0.67 6 4 A 34 25 3 1.1 0.15 0.25 0.60 8 5 A 35 25 5 1.3 0.170.26 0.65 9 6 B 36 50 1 0.6 0.12 0.17 0.71 6 4 A 37 50 3 1.2 0.16 0.240.67 9 5 A 38 50 5 1.2 0.17 0.25 0.68 9 6 A

The results indicate that in order to exhibit excellent characteristicsof the non-thermoplastic polyimide film, particularly low thermalexpansion thereof, the total thickness of the thermoplastic polyimideresin films formed on both surfaces is preferably smaller than that ofthe non-thermoplastic polyimide film, more preferably ½ or less and mostpreferably ⅕ or less of the thickness of the non-thermoplastic polyimidefilm. It is important to determine the thickness in consideration ofboth these results and the thickness of a proper thermoplastic polyimideresin film determined according to the surface treatment type inExamples 1 to 9.

EXAMPLE 39

A rolled copper foil was laminated on each of both surfaces of alaminate with a structure Y/B/Y (Y was 3 μm in thickness, and B was 25μm in thickness) by the same method as in Examples 1 to 9. Then, bothcopper foils were completely removed to obtain a laminate comprising thesurface-treated thermoplastic polyimide resin film. Then, a circuit wasformed on the laminate by the method below.

First, via holes of 30 μm in inner diameter were formed to pass throughthe laminate using a UV-YAG laser, and then desmeared with apermanganate under the same conditions as in Examples 1 to 9. At thesame time, the thermoplastic polyimide resin was surface-treated. Next,electroless plating was performed to form a copper plated layer on thesurface of the thermoplastic polyimide resin and in the via holes. Next,a liquid photosensitive plating resist (THB320P manufactured by JapanSynthetic Rubber Co., Ltd.) was coated and then exposed to light with ahigh-voltage mercury vapor lamp through a mask to form a resist patternwith a L/S of 15 μm/15 μm. Then, electrolytic copper plating wasperformed to form a copper circuit on a surface portion in which theelectroless-plated copper film was exposed. The electrolytic copperplating was performed by pre-washing in 10% sulfuric acid for 30 secondsand then plating at room temperature for 40 minutes. The current densitywas 2 A/dm². The thickness of the electrolytic copper film was 10 μm.Next, the plating resist was removed with an alkaline remover, and theelectroless copper plated layer was removed with a sulfuricacid/hydrogen peroxide etchant to obtain a printed circuit board.

The resultant printed circuit board had a designed L/S value. Also, thecircuit pattern was strongly bonded with an adhesive strength of 8 N/cm.

EXAMPLE 40

A laminate having a structure X/A/Cu (X was 1 μm in thickness, A was 25μm in thickness, and a copper foil was 15 μm in thickness) was prepared.In this state, the layer X, i.e., the thermoplastic polyimide resinfilm, had not been subjected to surface treatment. Then, a circuit wasformed on the laminate by the method below.

Via holes were formed by applying a UV laser to the thermoplasticpolyimide resin film side so as to pass through the thermoplasticpolyimide resin film and the non-thermoplastic polyimide film and extendto the copper foil, and then desmeared with a permanganate under thesame conditions as in Examples 1 to 9. At the same time, thethermoplastic polyimide resin was surface-treated. Next, electrolesscopper plating and electrolytic copper plating were performed. Next, adry film resist (Asahikasei dry resist AQ) was coated on each copperlayer, and exposure and development were performed. Then, an ordinarysubtractive method was preformed to form a circuit with a L/S of 25μm/25 μm on the surface of the thermoplastic polyimide resin and acircuit with a L/S of 100 μm/100 μm on the surface of the copper foil.As an etchant, an aqueous ferric chloride solution was used.

The resultant printed circuit board had a designed L/S value. Also, thecircuit pattern was strongly bonded with an adhesive strength of 7 N/cm.

EXAMPLE 41

A rolled copper foil was laminated on either surface of a laminatehaving a structure X/B/X (X was 3 μm in thickness, and B was 25 μm inthickness) by the same method as in Examples 1 to 9. Then, the copperfoils were completely removed to obtain the laminate comprising thesurface-treated thermoplastic polyimide resin films on both surfaces. Acircuit was formed on the laminate by the following method: First, viaholes of 30 μm in inner diameter were formed using a UV-YAG laser so asto pass through the laminate. Next, electroless plating was performed toform copper plated films on the surface of the thermoplastic polyimideresin and in the via holes. Then, electrolytic copper plating isperformed to form a copper plated layer having a thickness of 10 μm. Theelectrolytic copper plating was performed by pre-washing in 10% sulfuricacid for 30 seconds and then plating at room temperature for 40 minutes.The current density was 2 A/dm².

Next, a liquid photosensitive plating resist (THB320P manufactured byJapan Synthetic Rubber Co., Ltd.) was coated and then exposed to lightwith a high-voltage mercury vapor lamp through a mask to form a resistpattern with a L/S of 20 μm/20 μm. Then, an ordinary subtractive method(chemical: ferric chloride) was preformed using the resulting pattern toform a circuit.

The resultant printed circuit board had a designed L/S value. Also, thecircuit pattern was strongly bonded with an adhesive strength of 8 N/cm.

EXAMPLE 42

The polyamic acid solution prepared by Preparation Y was applied to oneof the surfaces of the non-thermoplastic polyimide film C of 12.5 μm inthickness prepared by Preparation C of polyimide film to form alaminate. The thickness of the thermoplastic polyimide film was 3 μm.Next, a rolled copper foil was laminated on one of the surfaces of theresultant laminate by the same method as in Examples 1 to 9. Then, anadhesive layer (12 μm) was applied to the non-thermoplastic polyimidefilm side to obtain a laminate comprising the copper foil layer, thethermoplastic polyimide resin film, the polyimide film, and the adhesivelayer. The thus-obtained laminate was laminated on an inner circuitboard prepared from a glass epoxy copper-clad laminate, and then cured.The lamination method was as described above.

Next, surface treatment was performed by dissolving off the copper foilwith a ferric chloride etchant to form irregularity on the surface ofthe thermoplastic polyimide resin film. Then, via holes of 30 μm ininner diameter were formed using a UV-YAG laser so as to extend to theinner circuit, and then desmeared with a permanganate under the sameconditions as in Examples 1 to 9. At the same time, the thermoplasticpolyimide resin was surface-treated. Next, electroless plating wasperformed to form electroless copper plated films on the surface of thethermoplastic polyimide resin and in the via holes.

Next, a liquid photosensitive plating resist (THB320P manufactured byJapan Synthetic Rubber Co., Ltd.) was coated and then exposed to lightwith a high-voltage mercury vapor lamp through a mask to form a resistpattern with a L/S of 15 μm/15 μm. Then, electrolytic copper plating isperformed to form a copper circuit on a surface portion where theelectroless-plated copper film was exposed. The electrolytic copperplating was performed by pre-washing in 10% sulfuric acid for 30 secondsand then plating at room temperature for 40 minutes. The current densitywas 2 A/dm². The thickness of the electrolytic copper film was 10 μm.Next, the plating resist was removed with an alkaline remover, and theelectroless-plated copper layer was removed with a sulfuricacid/hydrogen peroxide etchant to obtain a printed circuit board.

The resultant printed circuit board had a designed L/S value. Also, thecircuit pattern was strongly bonded with an adhesive strength of 8 N/cm.

EXAMPLE 43

The polyamic acid solution prepared by Preparation Y was applied to oneof the surfaces of the non-thermoplastic polyimide film C of 12.5 μm inthickness prepared by Preparation C of polyimide film to form alaminate. The thickness of the thermoplastic polyimide film was 1 μm.Next, an adhesive layer (12 μm) was applied to the non-thermoplasticpolyimide film side to obtain a laminate comprising the thermoplasticpolyimide resin film Y, the polyimide film C, and the adhesive layer.The thus-obtained laminate was laminated on an inner circuit boardprepared from a glass epoxy copper-clad laminate, and then cured.

Next, via holes of 30 μm in inner diameter were formed using a UV-YAGlaser so as to extend to the inner circuit, and then desmeared with apermanganate under the same conditions as in Examples 1 to 9. At thesame time, the thermoplastic polyimide resin was surface-treated. Next,electroless plating was performed to form electroless copper platedfilms on the surface of the thermoplastic polyimide resin and in the viaholes. Next, a liquid photosensitive plating resist (THB320Pmanufactured by Japan Synthetic Rubber Co., Ltd.) was coated and thenexposed to light with a high-voltage mercury vapor lamp through a maskto form a resist pattern with a L/S of 10 μm/10 μm. Then, electrolyticcopper plating is performed to form a copper circuit on a surfaceportion where the electroless-plated copper film was exposed. Theelectrolytic copper plating was performed by pre-washing in 10% sulfuricacid for 30 seconds and then plating at room temperature for 40 minutes.The current density was 2 A/dm². The thickness of the electrolyticcopper film was 10 μm. Next, the plating resist was removed with analkaline remover, and the electroless-plated copper layer was removedwith a sulfuric acid/hydrogen peroxide etchant to obtain a printedcircuit board. The resultant printed circuit board had a designed L/Svalue. Also, the circuit pattern was strongly bonded with an adhesivestrength of 7 N/cm.

(Preparation T of Thermoplastic Polyimide Precursor)

In a 2000-mL glass flask, one equivalent ofbis{4-(3-aminophenoxy)phenyl}sulfone (referred to as “BAPS-M”hereinafter) was dissolved in N,N-dimethylformamide (referred to as“DMF” hereinafter) in a nitrogen atmosphere. The resultant solution wasstirred under cooling with ice-water, and then one equivalent of4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) (referred toas “BPADA” hereinafter) was dissolved in the solution to obtain apolyamic acid polymer solution having a solid content of 30% by weight.

EXAMPLE 44

The polyamic acid polymer solution prepared by Preparation T was heatedunder a reduced pressure of 665 Pa at 200° C. for 3 hours to obtain asolid thermoplastic polyimide resin.

The resultant thermoplastic polyimide resin, a novolac epoxy resin(Epicoat 1032H60: manufactured by Yuka-Shell Company), and4,4′-diaminodiphenylsulfone (referred to as “4,4′-DDS” hereinafter) weremixed at a weight ratio of 90/10/3. Then, the resultant mixture wasdissolved in dioxolane so that the solid content was 20% by weight, toobtain a polyimide resin composition solution (a).

On the other hand, the resultant thermoplastic polyimide resin, anovolac epoxy resin (Epicoat 1032H60: manufactured by Yuka-ShellCompany), and 4,4′-diaminodiphenylsulfone (referred to as “4,4′-DDS”hereinafter) were mixed at a weight ratio of 50/50/15. Then, theresultant mixture was dissolved in dioxolan so that the solid contentwas 30% by weight, to obtain a polyimide resin composition solution(a2). The resulting solution was applied to a polyethylene terephthalatefilm of 125 μm in thickness used as a support so that the dry thicknesswas 25 μm, and then dried at 60° C. for 2 minutes and at 170° C. for 5minutes. Then, the coated film was removed from the polyethyleneterephthalate film to form an adhesive sheet (x).

The resulting polyimide resin composition solution (a) was applied toone of the surfaces of the non-thermoplastic polyimide film A of 25 μmin thickness so that the dry thickness was 4 μm, and then dried at 60°C. for 2 minutes and at 170° C. for 5 minutes to obtain a laminate. Theadhesive sheet (x) was laminated on the resulting laminate so that theadhesive sheet (x) faced the polyimide film of the laminate, and thensandwiched between two copper foil roughened surfaces (rolled copperfoils; BHY-22B-T manufactured by Japan Energy Co., Ltd., Rz=1.97 μm),followed by curing using a vacuum press under the conditions including atemperature of 200° C., a heat plate pressure of 1 MPa, a pressing timeof 1 hour, and a vacuum condition of 1 kPa. As a result, a curedlaminate was obtained. After the rolled copper foil on the layer (a) ofthe laminate was etched with a ferric chloride etchant, the adhesivestrength between the roughened surface and an electroless-plated copperlayer to the layer (a) was 8 N/cm. Also, the volume resistivity was2.0×10¹⁶ Ω·cm, the relative dielectric constant was 3.0, and thedielectric loss tangent was 0.011. These dielectric properties wereevaluated in a range of 1 to 10 GHz by a cavity resonator perturbationmethod using a complex dielectric constant evaluation apparatusmanufactured by KEAD Co., Ltd. The adhesive strength to the electrolessplated copper was measured as follows: First, electroless copper platingwas performed after etching of the rolled copper foil. Theelectroless-plated layer was formed to a thickness of 300 nm by the samemethod as shown in Table 1. Then, an electrolytic plated copper layerwas formed on the electroless-plated copper layer using a copper sulfateplating solution. The electrolytic copper plating was performed bypre-washing in 10% sulfuric acid for 30 seconds, and then plating atroom temperature for 40 minutes. The current density was 2 A/dm², andthe thickness of the film was 20 μm. The plated copper layer was etchedthrough a mask to form a conductor layer with a width of 3 mm. Theadhesive strength (peeling angle of 180°) of the conductor layer to thelayer (a) was measured according to JIS C6481.

(2) An inner circuit board was prepared from a glass epoxy copper-cladlaminate comprising a copper foil of 9 μm in thickness was formed. Then,the circuit surface of the circuit board, the layer (x), the laminatecomprising the non-thermoplastic polyimide film prepared in PreparationA and the layer (a), and a rolled copper foil (BHY-22B-T manufactured byJapan Energy Co., Ltd., Rz=1.97 μm) having a roughened surface thereonwere laminated with a vacuum press under the conditions including atemperature of 200° C., a heat plate pressure of 1 MPa, a pressing timeof 1 hour, and a vacuum condition of 1 kPa, and then cured. Thelamination was performed so that the layer (a) of the laminate faced therolled copper foil.

(3) The copper foil over the entire surface of the laminate obtained asdescribed above (2) was etched with a ferric chloride etchant.

(4) Via holes of 30 μm in inner diameter were formed directly above anelectrode of the inner board by a UV-YAG laser so as to extend to theelectrode.

(5) Then, electroless copper plating was performed over the entiresurface of the board by the following method: First, the laminate wascleaned with an alkali cleaner liquid and then pre-dipped in an acid fora short time. Furthermore, alkali reduction was performed in an alkalisolution in the presence of a palladium catalyst. Then, chemical copperplating was performed in an alkali at room temperature for 10 minutes.In this method, an electroless copper plated layer having a thickness of300 nm was formed.

(6) A liquid photosensitive plating resist (THB320P manufactured byJapan Synthetic Rubber Co., Ltd.) was coated and then dried at 110° C.for 10 minutes to form a resist layer of 20 μm in thickness. A glassmask with a L/S of 15 μm/15 μm was bonded to the resist layer and thenexposed to light with an ultraviolet exposure device comprising aextra-high-voltage mercury vapor lamp for 1 minute. Then, developmentwas performed by dipping in a developer (PD523AD manufactured by JapanSynthetic Rubber Co., Ltd.) for 3 minutes to remove the exposed portionto form a resist pattern with a L/S of 15 μm/15 μm.

(7) Then, a copper pattern of 10 μm in thickness was formed using acopper sulfate plating solution on the surface portion where theelectroless-plated copper film was exposed. The electrolytic copperplating was performed by pre-washing in 10% sulfuric acid for 30seconds, and then plating at room temperature for 20 minutes. Thecurrent density was 2 A/dm², and the thickness of the film was 10 μm.

(8) The plating resist was removed with acetone.

(9) The electroless-plated copper layer was removed from portions otherthan a circuit by dipping in a sulfuric acid/hydrogen peroxide etchantfor 5 minutes to form a printed circuit board.

The resultant printed circuit board substantially had a designed L/Svalue and a satisfactory circuit shape. As a result of EPMA analyticalmeasurement of a residual metal on a portion from which a feeding layerwas removed, no residual metal was observed. In addition, the roughenedsurface of the polyimide resin composition layer had a Rz value of 1.0μm, a Ra1 value of 0.13 μm, a Ra2 value of 0.23 μm, and a Ra1/Ra2 ratioof 0.57. Therefore, the circuit pattern was strongly bonded.

EXAMPLE 45

A cured laminate and a printed circuit board were produced by the samemethod as in Example 44 except that 1,3-bis(3-aminophenoxy)benzene(referred to as “APB” hereinafter) was used instead of BAPS-M used inPreparation T to form a polyimide resin composition solution (b). In thecured laminate, adhesive strength to an electroless-plated copper layerwas 7 N/cm. Also, the volume resistivity was 1.7×10¹⁶ Ω·cm, the relativedielectric constant was 3.0, and the dielectric loss tangent was 0.010.The resultant printed circuit board had substantially a designed L/Svalue and a satisfactory circuit shape. As a result of EPMA analyticalmeasurement of a residual metal on a portion from which a feeding layerwas removed, no residual metal was observed. In addition, the roughenedsurface of the polyimide resin composition layer had a Rz value of 1.1μm, a Ra1 value of 0.15 μm, a Ra2 value of 0.24 μm, and a Ra1/Ra2 ratioof 0.63. Therefore, the circuit pattern was strongly bonded.

EXAMPLE 46

A cured laminate and a printed circuit board were produced by the samemethod as in Example 44 except that 0.95 equivalent of APB and 0.05equivalent of 3,3′-dihydroxy-4,4′diaminobiphenyl were used instead ofone equivalent of BAPS-M used in Preparation T to form a polyimide resincomposition solution (c). In the cured laminate, adhesive strength to anelectroless-plated copper layer was 8 N/cm. Also, the volume resistivitywas 1.9×10¹⁶ Ω·cm, the relative dielectric constant was 3.1, and thedielectric loss tangent was 0.010. The resultant printed circuit boardhad substantially a designed L/S value and a satisfactory circuit shape.As a result of EPMA analytical measurement of a residual metal on aportion from which a feeding layer was removed, no residual metal wasobserved. In addition, the roughened surface of the polyimide resincomposition layer had a Rz value of 1.1 μm, a Ra1 value of 0.15 μm, aRa2 value of 0.23 μm, and a Ra1/Ra2 ratio of 0.65. Therefore, thecircuit pattern was strongly bonded.

EXAMPLE 47

A cured laminate and a printed circuit board were produced by the samemethod as in Example 44 except that in Preparation T, the polyimideresin composition solution (a) was applied to both surfaces of thepolyimide film so that the dry thickness of each layer was 4 μm. In thecured laminate, adhesive strength to an electroless-plated copper layerwas 8 N/cm. Also, the volume resistivity was 2.1×10¹⁶ Ω·cm, the relativedielectric constant was 3.0, and the dielectric loss tangent was 0.011.The resultant printed circuit board had substantially a designed L/Svalue and a satisfactory circuit shape. As a result of EPMA analyticalmeasurement of a residual metal on a portion from which a feeding layerwas removed, no residual metal was observed. In addition, the roughenedsurface of the polyimide resin composition layer had a Rz value of 1.0μm, a Ra1 value of 0.13 μm, a Ra2 value of 0.24 μm, and a Ra1/Ra2 ratioof 0.54. Therefore, the circuit pattern was strongly bonded.

EXAMPLE 48

The polyimide resin composition solution (a2) prepared using thepolyamic acid polymer solution in Preparation T was applied to a surfaceof a laminate comprising the non-thermoplastic polyimide resin film A(referred to as “layer A” hereinafter) and the layer (a) so that thesurface was opposite to the layer (a) and the dry thickness was 25 μm,and then dried at 60° C. for 2 minutes and at 170° C. for 5 minutes toform a layer (s). As a result, a laminate comprising the layer (s), thelayer (A), and the layer (a) was obtained.

A cured laminate was produced by the same method as in Preparation Texcept that the resultant laminate was sandwiched between the roughenedsurfaces of two copper foils (rolled copper foil BHY-22B-T manufacturedby Japan Energy Co., Ltd., Rz=1.97 μm). In addition, a printed circuitboard was produced by the same method as in Example 44(2) except that acircuit surface of an inner circuit board, the laminate comprising thelayer (s) and the non-thermoplastic polyimide film prepared inPreparation A, and the layer (a), and a rolled copper foil (BHY-22B-Tmanufactured by Japan Energy Co., Ltd., Rz=1.97 μm) with a roughenedsurface were laminated so that the roughened surface faced the laminate.In the cured laminate, adhesive strength to an electroless-plated copperlayer was 8 N/cm. Also, the volume resistivity was 2.0×10¹⁶ Ω·cm, therelative dielectric constant was 3.0, and the dielectric loss tangentwas 0.011. The resultant printed circuit board had substantially adesigned L/S value and a satisfactory circuit shape. As a result of EPMAanalytical measurement of a residual metal on a portion from which afeeding layer was removed, no residual metal was observed. In addition,the roughened surface of the polyimide resin composition layer had a Rzvalue of 1.0 μm, a Ra1 value of 0.14 μm, a Ra2 value of 0.23 μm, and aRa1/Ra2 ratio of 0.61. Therefore, the circuit pattern was stronglybonded.

EXAMPLE 49

A cured laminate and a printed circuit board were produced by the samemethod as in Example 44 except that in Preparation T, the thermoplasticpolyimide resin was mixed with an oligomer BA200 (trade name,manufactured by Lonza Inc.) of cyanate ester PRIMASET BADCY (trade name,manufactured by Lonza Inc.) and zinc (II) acetylacetonate were mixed ata weight ratio of 90/10/0.004 instead of being mixed with novolac epoxyresin (Epicoat 1032H60: manufactured by Yuka-Shell Company) and4,4′-diaminodiphenylsulfone (referred to as “4,4′-DDS” hereinafter) at aweight ratio of 90/10/3, to form a polyimide resin composition solution(d). In the cured laminate, adhesive strength to an electroless-platedcopper layer was 7 N/cm. Also, the volume resistivity was 2.0×10¹⁶ Ω·cm,the relative dielectric constant was 2.9, and the dielectric losstangent was 0.009. The resultant printed circuit board had substantiallya designed L/S value and a satisfactory circuit shape. As a result ofEPMA analytical measurement of a residual metal on a portion from whicha feeding layer was removed, no residual metal was observed. Inaddition, the roughened surface of the polyimide resin composition layerhad a Rz value of 0.9 μm, a Ra1 value of 0.12 μm, a Ra2 value of 0.21μm, and a Ra1/Ra2 ratio of 0.57. Therefore, the circuit pattern wasstrongly bonded.

EXAMPLE 50

A cured laminate and a printed circuit board were produced by the samemethod as in Example 44 except that the polyimide resin compositionsolution (a) was applied to one of the surfaces of the non-thermoplasticpolyimide film of 12.5 μm in thickness prepared in Preparation A so thatthe dry thickness of each layer was 1 μm instead of being applied on oneof the surfaces of the non-thermoplastic polyimide film of 25 μm inthickness so that the dry thickness was 4 μm. In the cured laminate,adhesive strength to an electroless-plated copper layer was 7 N/cm.Also, the volume resistivity was 1.8×10¹⁶ Ω·cm, the relative dielectricconstant was 3.0, and the dielectric loss tangent was 0.011. Theresultant printed circuit board had substantially a designed L/S valueand a satisfactory circuit shape. As a result of EPMA analyticalmeasurement of a residual metal on a portion from which a feeding layerwas removed, no residual metal was observed. In addition, the roughenedsurface of the polyimide resin composition layer had a Rz value of 1.0μm, a Ra1 value of 0.13 μm, a Ra2 value of 0.23 μm, and a Ra1/Ra2 ratioof 0.57. Therefore, the circuit pattern was strongly bonded.

EXAMPLE 51

A cured laminate and a printed circuit board were produced by the samemethod as in Example 44 except that a build-up substrate epoxy resinsheet (y) of 25 μm in thickness was used instead of the adhesive sheet(x) of 25 μm in thickness. In the cured laminate, adhesive strength toan electroless-plated copper layer was 8 N/cm. Also, the volumeresistivity was 1.5×10¹⁵ Ω·cm, the relative dielectric constant was 3.2,and the dielectric loss tangent was 0.014. The resultant printed circuitboard had substantially a designed L/S value and a satisfactory circuitshape. As a result of EPMA analytical measurement of a residual metal ona portion from which a feeding layer was removed, no residual metal wasobserved. In addition, the roughened surface of the polyimide resincomposition layer had a Rz value of 1.0 μm, a Ra1 value of 0.14 μm, aRa2 value of 0.24 μm, and a Ra1/Ra2 ratio of 0.58. Therefore, thecircuit pattern was strongly bonded.

COMPARATIVE EXAMPLE 6

An inner circuit board was produced using a glass epoxy copper-cladlaminate comprising a copper foil of 9 μm in thickness, and then thebuild-up substrate epoxy resin sheet (y) of 50 μm in thickness waslaminated on the circuit board, followed by curing at 170° C. for 30minutes. Next, the resulting insulating board was dipped in a potassiumpermanganate solution for 10 minutes to roughen the surface of the resinlayer, for improving adhesiveness to an electroless-plated film. Next, acured laminate and a printed circuit board were produced by the sameprocedures as in Example 44(4) and the subsequent steps. In the curedlaminate, adhesive strength to an electroless-plated copper layer was 7N/cm. Also, the volume resistivity was 4.0×10¹³ Ω·cm, the relativedielectric constant was 3.5, and the dielectric loss tangent was 0.040.In addition, the roughened surface of the polyimide resin compositionlayer had a Rz value of 3.5 μm, a Ra1 value of 0.19 μm, a Ra2 value of0.58 μm, and a Ra1/Ra2 ratio of 0.33. Although the circuit pattern wasstrongly bonded, the circuit width varied because of the largeirregularity on the resin surface of the resultant printed circuitboard. Also, as a result of EPMA analytical measurement of a residualmetal on a portion from which a feeding layer was removed, copper wasobserved.

COMPARATIVE EXAMPLE 7

An inner circuit board was produced using a glass epoxy copper-cladlaminate comprising a copper foil of 9 μm in thickness, and then thebuild-up substrate epoxy resin sheet (z) of 45 μm in thickness waslaminated on the circuit board, followed by curing at 160° C. for 60minutes. Next, the resulting insulating board was dipped in a potassiumpermanganate solution for 2 minutes to roughen the surface of the resinlayer, for improving adhesiveness to an electroless-plated film. Next, acured laminate and a printed circuit board were produced by the sameprocedures as in Example 44(4) and the subsequent steps. In the curedlaminate, adhesive strength to an electroless-plated copper layer was 2N/cm. Also, the volume resistivity was 5.0×10¹³ Ω·cm, the relativedielectric constant was 3.7, and the dielectric loss tangent was 0.042.The resultant printed circuit board had substantially a designed L/Svalue and a satisfactory circuit shape. As a result of EPMA analyticalmeasurement of a residual metal on a portion from which a feeding layerwas removed, no residual metal was observed. However, the circuitpattern on the printed circuit board was easily removed. The roughenedsurface of the polyimide resin composition layer had a Rz value of 1.2μm, a Ra1 value of 0.04 μm, a Ra2 value of 0.18 μm, and a Ra1/Ra2 ratioof 0.22.

REFERENCE EXAMPLE 1

The polyimide resin composition solution (a) was applied to a thicknesson a polyethylene terephthalate film of 125 μm in thickness used as asupport so that the dry thickness was 50 μm, and then dried at 80° C.for 2 minutes, at 120° C. for 2 minutes, and at 170° C. for 2 minutes toobtain a polyimide resin sheet. The support was separated from the sheetto obtain a single-layer sheet, and the sheet was sandwiched between theroughened surfaces of two copper foils (rolled copper foil; BHY-22B-Tmanufactured by Japan Energy Co., Ltd., Rz=1.97 μm). Then, curing wasperformed by a vacuum press under the conditions including a temperatureof 200° C., a heat plate pressure of 3 MPa, a pressing time of 1 hour,and a vacuum condition of 1 kPa to obtain a cured laminated. Afteretching of the rolled copper foil, adhesive strength of the roughenedsurface of the layer (a) to an electroless-plated copper layer was 8N/cm. Also, the volume resistivity was 1.7×10¹⁶ Ω·cm, the relativedielectric constant was 3.1, and the dielectric loss tangent was 0.012.Then, a printed circuit board was produced by the same operation as inExample 44(2) except that a circuit plane of an inner circuit board, thesingle layer sheet, and a rolled copper foil (BHY-22B-T manufactured byJapan Energy Co., Ltd., Rz=1.97 μm) with a roughened surface werelaminated so that the roughened surface faced the sheet, and cured by avacuum press under the conditions including a temperature of 200° C., aheat plate pressure of 3 MPa, a pressing time of 1 hour, and a vacuumcondition of 1 kPa. The resultant printed circuit board hadsubstantially a designed L/S value and a satisfactory circuit shape. Asa result of EPMA analytical measurement of a residual metal on a portionfrom which a feeding layer was removed, no residual metal was observed.Furthermore, the roughened surface of the polyimide resin compositionlayer had a Rz value of 1.0 μm, a Ra1 value of 0.14 μm, a Ra2 value of0.24 μm, and a Ra1/Ra2 ratio of 0.58, and the circuit was stronglybonded.

TABLE 6 Polyimide resin Compositin Thickness of each compositin PolymerCompositin of of cured compositin of example solution film Adhesiveformed laminate laminate cured laminate 44 (a) A (x) layer(a)/Alayer(a)/A/ 4 μm/25 μm/ (x) 25 μm 45 (b) A (x) layer(b)/A layer(b)/A/ 4μm/25 μm/ (x) 25 μm 46 (c) A (x) layer(c)/A layer(c)/A/ 4 μm/25 μm/ (x)25 μm 47 (a) A (x) layer(a)/A/ layer(a)/A/ 4 μm/25 μm/ layer(a)layer(a)/(x) 4 μm/25 μm 48 (a) A • layer(a)/A/ layer(a)/A/ 4 μm/25 μm/layer(s) layer(s) 25 μm 49 (d) A (x) layer(d)/A layer(d)/A/ 4 μm/25 μm/(x) 25 μm 50 (a) A (x) layer(a)/A layer(a)/A/ 1 μm/12.5 μm/ (x) 25 μm 51(a) A (y) layer(a)/A layer(a)/A/ 4 μm/25 μm/ (y) 25 μm Comparative • •(y) • (y) 50 μm Example 6 Comparative • • (z) • (z) 45 μm Example 7Reference (a) • • • (a) 50 μm Example 1

TABLE 7 Cured laminate Peel strength to non- Printed circuit boardelectroless Relative dielectric Volume Surface Adhesiveness coated steelconstant/dielectric resistvity Roughness to circuit Residual Shape ofexample (N/cm) loss tangent (Ω · cm) (μm) board metal circuit 44 83.0/0.011 2.0 × 10¹⁶ 1.0 Good None Good 45 7 3.0/0.010 1.7 × 10¹⁶ 1.1Good None Good 46 8 3.1/0.010 1.9 × 10¹⁶ 1.1 Good None Good 47 83.0/0.011 2.1 × 10¹⁶ 1.0 Good None Good 48 8 3.0/0.011 2.0 × 10¹⁶ 1.0Good None Good 49 7 2.9/0.009 2.0 × 10¹⁶ 0.9 Good None Good 50 73.0/0.011 1.8 × 10¹⁶ 1.0 Good None Good 51 8 3.2/0.014 1.5 × 10¹⁵ 1.0Good None Good Comparative 7 3.5/0.040 4.0 × 10¹³ 3.5 Good Residue Nogood Example 6 Comparative 2 3.7/0.042 5.0 × 10¹³ 1.2 No good None Nogood Example 7 Reference 8 3.1/0.012 1.7 × 10¹⁶ 1.0 Good None GoodExample 1

EXAMPLE 52

A roughened surface (Ra2=0.28 μm) of a rolled copper foil BHY-22B-T (18μm, manufactured by Japan Energy Co., Ltd.) was placed on athermoplastic polyimide layer of a laminate comprising the polyimidefilm C of 25 μm in thickness and the thermoplastic polyimide resin layerZ, and laminated by a heat roll under the conditions including atemperature of 310° C., a linear pressure of 20 kgf, and a processingvelocity of 1.5 m/min. The laminated copper foil was completely removedwith a hydrochloric acid/ferric chloride etchant to obtain a resinsurface roughened with the copper foil. Next, the roughened resinsurface was treated with a surface treatment agent (referred to as a“desmearing liquid”) comprising a permanganate under the same conditionsas shown in Table 2 except that the treatment time of each of swelling,microetching, and neutralization was changed from 2 minutes to 5minutes, to obtain a laminate comprising a surface-roughenedthermoplastic polyimide resin film according to the present invention.The surface shape of the resulting laminate was observed. The resultsare shown in Table 7.

Then, electroless copper plating and electrolytic copper plating wereperformed on the roughened surface to form a copper layer of 18 μm inthickness, and adhesiveness at room temperature was measured. Theresults are shown in Table 3.

Furthermore, a resist pattern was formed on the copper plated layer, andthe exposed portion of the plated copper layer was removed with ahydrochloric acid/ferric chloride etchant to form wiring with a L/S of10 μm/10 μm. The thus-formed wiring was observed through an opticalmicroscope to measure the circuit shape and the presence of etchingresidue of copper. The results are shown in Table 3.

(Preparation S of Thermoplastic Polyimide Laminate)

In DMF, 1,3-bis(3-aminophenoxy)benzene and 3,3′-dihydroxybenzidinedissolved at a molar ratio of 4:1, and4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) was addedunder stirring so that the acid dianhydride and the diamine becameequimolar. The resultant mixture was stirred for about 1 hour to preparea polyamic acid DMF solution with a solid content of 20% by weight.

The resultant DMF solution of polyamic acid, which is a precursor ofthermoplastic polyimide, was applied to one of the surfaces of thenon-thermoplastic polyimide film A by a gravure coater, the polyimidefilm A being prepared in Preparation A and used as a core film.

After the application, heating treatment was performed at a finalheating temperature of 390° C. to remove the solvent or imidize thepolyamic acid, thereby producing a laminated polyimide film comprising anon-thermoplastic polyimide layer and a thermoplastic polyimide layer.The thickness of the thermoplastic polyimide layer was adjusted bycontrolling the coating amount so as to be 4 μm after dryingimidization. The measured glass transition temperature of the singlesheet of the thermoplastic polyimide resin was 180° C.

EXAMPLE 53

A surface of the thermoplastic polyimide layer of the laminate preparedin Preparation S was treated with a desmearing liquid to obtain alaminate comprising a surface-roughened thermoplastic polyimide resinfilm according to the present invention. The treatment with thedesmearing liquid was carried out by the same method as in Example 1except that the treatment time in each step was changed to 5 minutes.

Then, surface analysis, formation of a plated copper layer, formation ofmicro-wiring, and evaluation of circuit formability, adhesiveness, andetching residue of the metal used were conducted by the same methods asin Example 52.

EXAMPLE 54

A roughened surface (Ra2=0.59 μm) of a rolled copper foil F2-WS (12 μm,manufactured by Furukawa Electric Co., Ltd.) was placed on thethermoplastic polyimide layer of the laminate prepared by theabove-described method, and laminated by a heat roll under theconditions including a temperature of 310° C., a linear pressure of 20kgf, and a processing velocity of 1.5 m/min. The laminated copper foilwas completely removed with a hydrochloric acid/ferric chloride etchantto obtain a resin surface roughened with the copper foil. The observedsurface shape of the resulting resin surface was as shown in Table 3.Then, surface analysis, formation of a plated copper layer, formation ofmicro-wiring, and evaluation of circuit formability, adhesiveness, andetching residue of the metal used were conducted by the same methods asin Example 52.

EXAMPLE 55

Surface analysis, formation of a plated copper layer, formation ofmicro-wiring, and evaluation of circuit formability, adhesiveness, andetching residue of the metal used were conducted by the same methods asin Example 52 except that a roughened surface (Ra2=0.28 μm) of a copperfoil TQ-VLP (9 μm, manufactured by Mitsui Mining and Smelting Company)was used.

EXAMPLE 56

The surface of the thermoplastic polyimide layer of the laminateprepared by the above-described method was embossed by an embossing roll(made of stainless with Ra2 =0.72 μm, backup roll: hardness SHEER D-78)at a temperature of 220° C., a linear pressure of 100 kgf/cm, and aprocessing velocity of 2 m/min. The resulting roughened surface wastreated with a desmearing liquid to obtain a laminate having asurface-roughened thermoplastic polyimide resin film according to thepresent invention. The treatment with the desmearing liquid was carriedout by the same method as in Example 52 except that the treatment timein each step was changed to 5 minutes.

Then, surface analysis, formation of a plated copper layer, formation ofmicro-wiring, and evaluation of circuit formability, adhesiveness, andetching residue of the metal used were conducted by the same methods asin Example 52.

EXAMPLE 57

The surface of the thermoplastic polyimide layer of the laminateprepared by the above-described method was polished (pressure current1.50 to 1.75 A, buff: Ra2=17 μm). The resulting roughened surface astreated with a desmearing liquid to obtain a laminate having asurface-roughened thermoplastic polyimide resin film according to thepresent invention. The treatment with the desmearing liquid was carriedout by the same method as in Example 52.

Then, surface analysis, formation of a plated copper layer, formation ofmicro-wiring, and evaluation of circuit formability, adhesiveness, andetching residue of the metal used were conducted by the same methods asin Example 52. The results are shown in Table 8.

TABLE 8 Circuit Ra1 Ra2 Ra1/ formability(※) Adhesiveness Example (μm)(μm) Ra2 Metal Circuit (N/cm) 52 0.14 0.23 0.61 None Good 12 53 0.060.07 0.85 None Good 8 54 0.27 0.39 0.69 None Good 11 55 0.19 0.29 0.66None Good 9 56 0.11 0.20 0.55 None Good 8 57 0.71 1.20 0.59 None Good 12(※)Circuit formability Circuit: Good means the pitch of edges in anypart of circuit is between 9 μm and 11 μm, and it means no good that thepitch become not more than 9 μm or not less than 11 μm. Metal: Nonemeans no copper signal is observed as good result, Copper signal meansmetal residue as bad result.

INDUSTRIAL APPLICABILITY

A thermoplastic polyimide resin film and laminate of the presentinvention permit formation of micro-wiring with low L/S, for example, aL/S of 30 μm/30 μm or less, and can be suitably used for manufacturingcircuit boards with excellent adhesiveness and heat resistance, such asa flexible printed circuit board (FPC) and a build-up circuit board. Amethod for manufacturing a circuit board of the present invention iscapable of satisfactorily forming a microcircuit pattern on a resincomposition surface according to the present invention even underlamination conditions such as a relatively low pressure. Also, themethod can provide a printed circuit board with high adhesive strength.

1. A resin film comprising a thermoplastic polyimide resin having asurface shape formed on at least one of the surfaces thereof, thesurface shape having a Ra1 value of arithmetic mean roughness of 0.05 μmto 1 μm measured with a cutoff value of 0.002 mm, and a Ra1/Ra2 ratio of0.4 to 1, Ra2 being a value measured with a cutoff value of 0.1 mm. 2.The resin film according to claim 1, comprising a polyimide resin.
 3. Alaminate comprising at least one layer of the resin film according toclaim
 1. 4. The laminate according to claim 1 further comprising a metallayer provided on the surface having the surface shape.